Recently user-oriented online sharing communities have seen explosive growth. Two characteristics of these communities set them apart from traditional online message-based communities such as online forums. First, users have no social ties before joining the community. Second, there is little or...

Online peer-to-peer communities and online social networks have become increasingly popular. In particular, the recent boost of online peer-to-peer communities leads to exponential growth in sharing of user-contributed content which have brought profound changes to business and economic...

Indirect reciprocity is an important factor that motivates individual contributions in social networks. However, prior studies of indirect reciprocity are often limited to a snapshot view of individual interactions in social environments. This paper analyzes indirect reciprocity from a dynamic...