How to Design a Reputation System: It’s All About Karma

Randy Farmer (@frandallfarmer) and Bryce Glass (@soldierant) share some insightful tips on designing web reputation, or karma, systems:

- Karma is user reputation within a context
- Karma is useful for building trust between users, and between a user and the site
- Karma can be an incentive for participation and contributions
- Karma is contextual and has limited utility globally. [A chessmaster is not a good eBay Seller]
- Karma comes in several flavors – Participation, Quality and Robust (combined)
- Karma should be complex and the result of indirect evaluations, and the formulation is often opaque
- Personal karma is displayed only to the owner, and is good for measuring progress
- Corporate karma is used by the site operator to find the very best and very worst users
- Public karma is displayed to other users, which is what makes it the hardest to get right
- Public karma should be used sparingly – it is hard to understand, isn’t expected, and is easily confused with content ratings
- Negative public karma should be avoided all together. In karma-math -1 is not the same magnitude as +1, and information loss is too expensive.
- Public karma often encourages competitive behavior in users, which may not be compatible with their motivations. This is most easily seen with leaderboards, but can happen any time karma scores are prominently displayed. [i.e.: Twitter follower count]

Their O’Reilly Media book Building Web Reputation Systems came out in March 2010.

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