This book constitutes the refereed proceedings of the Second International Conference on Social Informatics, SocInfo 2010, held in Laxenburg, Austria, in October 2010. The 17 revised full papers presented were carefully reviewed and selected from numerous submissions and feature both the theoretical social network analysis and its practical applications for social recommendation as well as social aspects of virtual collaboration, ranging from social studies of computer supported collaborative work, to the study of enhancements of the Wiki technology. Further topics are research on Webmining, opinion mining, and sentiment analysis; privacy and trust; computational social choice; and virtual teamwork.