• Create an incentive for good behavior. If participants know that they will be rated and that the rating is publicly available, they are more likely to provide accurate information (e.g., product listings), good service, and so on.

• Provide a selection effect. If participants know that good behavior will be noticed and rewarded, they are more likely to join the system. Similarly, would-be malicious participants will know that any incompetence or deliberate disruption will be made public—a deterrent to misbehavior.

Resnick cited two main challenges to reputation systems: the ability to create new pseudonyms and the high cost or other barriers to entry for newcomers. Most online sites use pseudonyms, and there are several valid reasons for not requiring “real” names.1 A user of a reputation system who develops a bad reputation can often easily create a new pseudonym. However, reputation systems can still succeed even when users are easily able to create pseudonyms, because those that establish positive reputations will continue to use their account, thus ensuring that positive information is available in the system. Similarly, a user who establishes a positive reputation has a disincentive to suddenly shift behaviors. The lack of reputation limits that user’s ability to participate in transactions since having a high approval rating with one transaction is much less valuable than having a high approval rating with 200 transactions.

Resnick also noted that the low value of having little or no reputation information creates barriers for newcomers. Research shows that it is not likely that one can treat each newcomer as having a positive reputation until they misbehave: when newcomers are treated as if they have a positive reputation, system managers become overwhelmed with the number of new, poorly behaved users that must be removed from the system. As a result, there seems to be no alternative to having newcomers pay their dues by developing a positive reputation over time. This tradeoff, between the utility of a well-managed reputation system and the high cost to newcomers, is a challenge to the growth of a reputation system, said Resnick.

Turning to the usefulness of reputation systems in the context of disaster response, Resnick commented that some participants may be able to develop a positive reputation through interactions before a disaster occurs, whereas other participants who may in fact have very useful information will not necessarily have established a prior reputation nor be able to establish their reputation quickly during an event. In such cases, additional measures are needed.

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1 For example, see National Research Council, The Internet’s Coming of Age, National Academy Press, Washington, D.C., 2001.



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