MIT Press book “The Reputation Society” (containing a chapter by me) is out!

The MIT Press I contributed to with a chapter is out! It is titled “The Reputation Society: how online opinions are reshaping the offline world” and edited by Hassan Masum and Mark Tovey.
It is available on MIT press and on Amazon.
The chapter I wrote is titled Trust It Forward: Tyranny of the Majority or Echo Chambers? and on it I ramble about objectivity/subjectivity, minorities/majorities, etc.

If reputation systems weight all perspectives similarly, they may devolve into simple majority rule. But if they give each user reputation scores that take only other similar users’ opinions into account, they run the risk of becoming “echo chambers” in which like-minded people reinforce each others’ views without being open to outside perspectives. Massa discusses design choices and trust metrics that may help balance these two extremes and the broader implication for our future societies.

the reputation society book cover The book received endorsements by people I really admire.
“As our societies expand from local villages to global networks, our ways of assessing and sharing reputation—the foundation of trust and community—must also evolve, but how? The thoughtful and thought-provoking essays in The Reputation Society bring a wide range of perspectives to this question, including the design of technological solutions, applications in philanthropy, science and governance, and warnings about the loss of privacy and autonomy. It is a fascinating collection of readings not only for scholars, but for anyone interested in the dynamics of the reviews and recommendations that shape our decisions—or in the future of how we will judge and be judged.”
Judith Donath, Fellow, Berkman Center for Internet and Society, Harvard University

“Today is tomorrow’s yesterday. These provocative essays, by some of the leading thinkers in the domain of reputation systems, illuminate how reputations regulate actions across time and social distance and point to the opportunities and obstacles that reputation systems present for commerce and democracy.”
Paul Resnick, Professor, University of Michigan School of Information

“The Reputation Society enriches the discussion of reputation by bringing together technologists, philosophers, legal scholars, and industry leaders to sort through the promise and perils we face today. It covers the practical, for those interested in the nuts and bolts of the challenges we face today, and the theoretical, for those looking to engage in broader discussions of the ethical and moral concerns. In short, a terrific and enlightening read!”
Danielle Keats Citron, Professor of Law, University of Maryland School of Law

The list of my co-authors is also very delightful.
Trust, reputation systems, and the immune system of democracy / Craig Newmark
Building the reputation society / Hassan Masum, Mark Tovey, & Yi-Cheng Zhang
Designing reputation systems for the social web / Chrysanthos Dellarocas
Web reputation systems and the real world / Randy Farmer
An inquiry into effective reputation and rating systems / John Henry Clippinger
The biology of reputation / John Whitfield
Regulating reputation / Eric Goldman
Less regulation, more reputation / Lior Strahilevitz
The role of reputation systems in managing online communities / Cliff Lampe
Attention philanthropy : giving reputation a boost / Alex Steffen
Making use of reputation systems in philanthropy / Marc Maxson & Mari Kuraishi
The measurement and mismeasurement of science / Michael Nielsen
Usage-based reputation metrics in science / Victor Henning, Jason Hoyt, and Jan Reichelt
Open access and academic reputation / John Willinsky
Reputation-based governance and making states “legible” to their citizens / Lucio Picci
Trust it forward : tyranny of the majority or echo chambers? / Paolo Massa
Rating in large-scale argumentation systems / Luca Iandoli, Josh Introne, & Mark Klein
Privacy, context, and oversharing : reputational challenges in a Web 2.0 world / Michael Zimmer & Anthony Hoffman
The future of reputation networks / Jamais Cascio
“I hope you know this is going on your permanent record” / Madeline Ashby & Cory Doctorow.

The cover of the book reads as follows.

In making decisions, we often seek advice. Online, we check Amazon recommendations, eBay vendors’ histories, TripAdvisor ratings, and even our elected representatives’ voting records. These online reputation systems serve as filters for information overload. In this book, experts discuss the benefits and risks of such online tools.

The contributors offer expert perspectives that range from philanthropy and open access to science and law, addressing reputation systems in theory and practice. Properly designed reputation systems, they argue, have the potential to create a “reputation society,” reshaping society for the better by promoting accountability through the mediated judgments of billions of people. Effective design can also steer systems away from the pitfalls of online opinion sharing by motivating truth-telling, protecting personal privacy, and discouraging digital vigilantism.

Designing Your Reputation System and Designing Social Interfaces

10 practical questions for designing a reputation system. This talk was (partially!) given at the 2008 IA Summit. By Bryce Glass on Slideshare

Designing Social Interfaces – workshop talk given at Web 2.0 Expo

My chapter in “Computing with Social Trust”

Computing with Social TrustThe book “Computing with Social Trust” is out. In it you can find a chapter by Paolo Avesani and myself about my PhD work on Trust in Recommender Systems. You can download my chapter or buy the dead-tree book from Amazon. Following you can find the Table of contents. Enjoy!


Continue Reading

First International Conference on Reputation: Theory and Technology – 18-20 March, 2009 – Gargonza, Italy.

1st International Conference on Reputation: Theory and Technology – ICORE 2009 aims to become a point of convergence in the multidisciplinary study of reputation.
It will be held in Gargonza Castle, Italy, in the heart of Tuscany, halfway between Siena and Arezzo, March 18-20, 2009

The role of reputation as a social artefact and its practical applications are coming more and more clearly to the attention of the scientific community. The study of reputation and gossip is important in many fields of the social sciences, for example organization science, policy-making, (e-)governance, cultural evolution, social dilemmas, socio-dynamics and sociobiology. Interest in reputation is increasing in philosophy, psychology, social psychology, sociology and cognitive science; formal models appear in game theoretical, mathematical and physics journals; computational reputation systems are among the most studied subjects in multi-agent technology and social simulations.

All this attention is timely, since reputation is an old concept for answering a new challenge, the regulation of complex, global, networked societies. Innovation demands that the potential of old instruments are fully understood and exploited, in order to be incorporated into novel, intelligent technologies.

However, there is a number of ad hoc models, and little integration of instruments for the implementation, management and optimisation of reputation. On the one hand, entrepreneurs and policy makers deem it possible to manage corporate and firm reputation without accessing a solid, general and integrated body of scientific knowledge on the subject. On the other hand, researchers believe they can discuss, design and implement reputation systems without investigating what properties, requirements and dynamics of reputation in natural societies are, and why they evolved.

Reputation deserves a full role as a scientific topic, a focus on its specificities, i.e., its potential as preventive social knowledge and selective mechanism of transmission.

We invite papers from all scientific communities working on reputation, including multi-agent systems, social simulation, economics, organisation science and management, e-governance/learning/business, virtual societies and markets, social cognition, (evolutionary) game theory, social psychology, sociology, social and collective dilemmas, social dynamics, cultural evolution and business ethics.

Topics for ICORE 2009 include but are not limited to:

* Theory of reputation
* Simulation of reputation
* Computational models of reputation
* Agent reputation models
* Ontologies of reputation
* Logical formalization of reputation
* Experimental evidence of reputation diffusion
* Reputation-based e-government, e-learning, e-business
* Reputation in p2p systems
* Reputation in grid environments
* Reputation for partner selection
* Incentives in Reputation Mechanisms
* Image and reputation
* Reputation management and optimisation
* Reputation and social networks
* Reputation and norms
* Reputation and altruism, reciprocity, and cooperation
* Reputation and trust
* Reputation for sabotage tolerance in large-scale applications
* Reputation and exchange
* Reputation and institutions
* Reputation and social capital
* Corporate and firm reputation

Submission instructions

Electronic submission will be added later to this website.

All submissions should be no longer than 15 pages, in pdf format.
Review criteria

Papers should present novel ideas related to reputation, clearly motivated by problems from current practice or applied research.
We expect claims to be substantiated by theoretical or formal analysis, experimental evaluations, comparative studies, and so on. Authors are also encouraged to submit application papers. Application papers are expected to address an indication of the real world relevance of the problem that is solved, including a description of the deployment domain, and some form of evaluation of performance, usability, or superiority to alternative approaches.
Important dates

* Abstract submission: September 15, 2008
* Paper submission: October 1st, 2008
* Notification: November 10, 2008
* Camera Ready Version of Accepted Papers: December 10, 2008
* Conference: March 18-20, 2009


The conference is organized with the support of the eRep project under the 6th FP of the European Community.

Linus Torvald is convinced version control should be based on trust networks

Thanks to Jesse, I started exploring Git, a version control system alternative to CVS and SVN. Git is based on a very different metaphor. While in CVS/SVN there is one repository which is maintained in a single location, in Git there are as many repositories as users and all of them are maintained in a decentralized fashion, on all the machines of all the users. From centralization to decentralization, it is an interesting twist and change in perspective.
And so what about the risk of balkanization of code? And the fact that there are 10.000 (different) versions of the Linux kernel? Well, according to Linus, the answer is trust. Linus explains the metaphores behind git and the trust issues in an extremely interesting Google Talk.

From the talk of Linux (via Victor):

The way merging is done is the way real security is done, by a network of trust. if you have ever done any security work and it didn’t involve the concept of network of trust it was not a security work; it was a masturbation.
…we don’t know hundred people. We have five, seven, ten close personal friends…

This way of managing a software ecology is wonderfully adhocratic. There are now thousands different versions of the Linux kernel. Currently most of the people rely on Linus’ version but it is possible, in a perfect adhocratic way, that different people will rely on versions of different people. Go decentralized, go trust-based. Cool.

Terrific slidecast about trust and reputation by Rentathing

By Rentathing. In a single slidecast, they explain clearly a possible and reasonable future society in which interactions are based on trust and reputation (someone would call it “whuffie”). And it even shows examples of ridesharing (letting other people benefit from your car) and couchsurfing (letting other people benefit from your house). A slidecast is worth thousands words.
UPDATE: As I was suggesting in the comments, read “Down and out in the magic kingdom” (Creative commons released so you can download it for free and much more) or just the Whuffie page in wikipedia: “Whuffie is the ephemeral, reputation-based currency of Cory Doctorow’s sci-fi novel, Down and Out in the Magic Kingdom.” BUT if you intend to read the book (suggested!!!), don’t read the wiki page!
And also check Ripple (really blowminding!) and its white paper “Money as IOUs in Social Trust Networks & A Proposal for a Decentralized Currency Network Protocol”.

Created with Admarket’s flickrSLiDR.

Edelman Trust Barometer 2007 presentation

If you are interested in Trust on a global scale, this presentation by Edelman titled “Edelman Trust Barometer 2007″ might be interesting for you.

More about the eBay feedback model and trust metrics attacks

My last post reminded myself of some paragraphs I wrote in a paper some time ago. I know my writing ability is not comparable to Shakespeare’s one but maybe you find some interesting information in this passage from A Survey of Trust Use and Modeling in Current Real Systems reported below:

EBay’s feedback ecology is a large and realistic example of a technology mediated market. The advantage of this is that a large amount of data about users’ interactions and behaviors can be recorded in a digital format and can be studied. In fact, there have been many studies on eBay and in particular on how the feedback system influences the market, see for example (Resnick and Zeckhauser, 2002). A very interesting observation is related to the distribution of feedback values: “Of feedback provided by buyers, 0.6% of comments were negative, 0.3% were neutral, and 99.1% were positive” (Resnick and Zeckhauser, 2002). This disproportion of positive feedbacks suggests two considerations: the first is actually a challenge and consists of verifying if these opinions are to be considered realistic or distorted by the interaction with the media and the interface. We will discuss this point later in Section 3. The second is about possible weaknesses of the eBay model. The main weakness of this approach is that it considers the feedback of every user with the same weight, and this could be exploited by the malicious user. Since on eBay there are so few negative feedbacks, a user with just few negative feedbacks is seen as highly suspicious and it is very likely nobody will risk into engaging in a commercial transaction with her. Moreover, having an established and reputable identity helps a lot the business activity. A controlled experiment on eBay (Resnick et al., 2003) found that an high reputation identity is able to get a selling price 7.6% higher than a newcomer identity with little reputation. For this reason, there are users who threaten to leave a negative feedback (and therefore destroy the other user’s reputation) unless they get a discount on their purchase.
This activity is called “feedback extortion” on eBay’s help pages (“EBay help: Feedback extortion”, n.d.) and in a November 2004 survey (Steiner, 2004) 38% of the total respondents stated that they had “received retaliatory feedback within the prior 6 months, had been victimized by feedback extortion, or both“.
These users are “attacking” the system: as eBay’s help page puts it “Feedback is the foundation of trust on eBay. Using eBay feedback to attempt to extort goods or services from another member undermines the integrity of the feedback system” (“EBay help: Feedback extortion”, n.d.). The system could defend itself by weighting in different ways the feedback of different users. For example, if Alice has been directly threatened by CoolJohn12 and thinks the feedback provided by him is not reliable, his feedback about other users should not be taken into account when
computing the trust Alice could place in the other users. In fact, a possible way to overcome this problem is to use Local Trust Metric (Massa and Avesani, 2005, Ziegler and Lausen, 2004), that considers only (or mainly) trust statements given by users trusted by the active user and not all the trust statements with the same, undifferentiated weight. In this way, receiving negative feedback from CoolJohn12 does not influence reputations as seen by the active user if the active user does not trust explicitly CoolJohn12. For a short discussion of Global and Local Trust Metrics, see Section 3. However, eBay at the moment uses the Global Trust Metric we described before, which is very simple. This simplicity is surely an advantage because it is easy for users to understand it and the big success of eBay is also due to the fact users easily understand how the system works and hence trust it (note that the meaning of “to trust” here means “to consider reliable and predictable an artifact” and not, as elsewhere on this chapter, “to put some degree of trust in another user”). Nevertheless, in November 2004, a survey on eBay’s feedback system (Steiner, 2004) found that only 3% of the respondents found it excellent, 19% felt the system was very good, 39% thought it was adequate and 39% thought eBay’s feedback system was fair or poor. These results are even more interesting when compared with numbers from a January 2003 identical survey. The portion of “excellent” went from 7% to 3%, the “very good” from 29% to 19%, the “adequate” from 35% to 39%, the “fair or poor” from 29% to 39%. Moreover, the portion of total respondents who stated that they had received retaliatory feedback within the prior 6 months passed from 27% of 2003 survey to 38% of 2004 survey. These shifts seem to suggest that the time might have come for more sophisticated (and, as a consequence, more complicated to understand) Trust Metrics.

Bibliography for this portion:
- Resnick, P., & Zeckhauser, R. (2002). Trust Among Strangers in Internet Transactions: Empirical Analysis of eBay’s Reputation System. The Economics of the Internet and Ecommerce. Advances in Applied Microeconomics, 11.
- Resnick, P., & Zeckhauser, R., & Swanson, J., & Lockwood, K. (2003). The value of reputation on eBay: A controlled experiment.
- eBay help: Feedback extortion. (n.d.) Retrieved December 28, 2005, from
- Steiner, D. (2004). Auctionbytes survey results: Your feedback on eBay’s feedback system. Retrieved December 28, 2005, from
- Massa, P., & Avesani, P. (2005). Controversial users demand local Trust Metrics: an experimental study on community. In Proceedings of 25th AAAI Conference.
- Ziegler, C., & Lausen, G. (2004). Spreading activation models for trust propagation. In IEEE International Conference on e-Technology, e-Commerce, and e-Service (EEE’04).

You can buy a positive feedback on eBay for 29 cents, so how much is it worth?

There is an interesting paper from John Morgan and Jennifer Brown of Berkeley which analyzes the Illicit “market for trust” on eBay. They onserved how on eBay there are a lot of listings with a Buy-It-Now option and a price of 1 penny. A Buy-It-Now sale for 1 cent automatically results in the seller losing 29 cents because eBay charges a 25-cent listing fee and 5 cents for the Buy-It-Now option. So, why should I sell something for 1 cent if this means I’m going to lose 29 cents? Well, basically I’m buying a positive feedback and paying it 29 cents. It is very interesting to note that the item being sold is actually a 1-cent “Free positive feedback ebook and recipe no shipping” which advised buying 100 different items on eBay that cost almost nothing in order to “get your feedback score up to 100 in just a few days.”
Free positive feedback ebook and recipe no shipping image.
(the image is from the same authors paper “Reputation in Online Markets: Some Negative Feedback”).
Does such a listing make sense? Well, it depends. The article goes on saying that the sellers, after getting a wonderful reputation, are probably going to move in very profitable markets such as selling cars or lands. For example, the authors found one particular seller, whom they dubbed the landseller, who had accumulated hundreds of feedback points by posting 304 offers for feedback enhancement on eBay (and losing $87.64). Then, after his feedback rating reached 598, the landseller went on to try to sell several parcels of undeveloped land in the southern U.S. on eBay.
This is one more example of a trust metric attack: every time someone provide a system based on reputation, some people will try to fool and attack it. No system is totally attack resistant. And this is uber interesting.