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...