Modern software architecting increasingly often takes place in geographically distributed contexts involving teams of professionals and customers with different backgrounds and roles. So far, attention and effort have been mainly dedicated to individuals sharing already formalized knowledge and less to social, informal collaboration. Furthermore, in Web 2.0 contexts, little to no attention has been given to practitioners carrying out complex, collaborative, and knowledge-intensive tasks in organizational contexts. This chapter shows how we can effectively support the combination of formal and informal collaboration and build a Virtual Community for architectural knowledge sharing. We present a set of collaboration scenarios that define a co...