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...

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...

Peer-to-peer sharing networks have seen explosive growth recently. In these networks, sharing files is completely voluntary, and there is no financial reward for users to contribute. Yet many users continue to share despite the massive free-riding by others. Using a large-scale dataset of...