Hello. :-) My thesis was actually about virtual communities in social networks. The idea was to explore how communities would appear in social networks, but not considering communities just an structure (as part of literature does) but also as a group of people with strong ties and social capital ( Rheingold's concept and sociological concepts). The original point was to track the structure of a cluster in the network of a social network site (in the end I just analyzed Fotolog, but I started with weblogs and Orkut as well) through reciprocal social interaction within the users (comments in fotologs and weblogs and scraps in Orkut). Then, after observing the network structure and identifying the nodes in the cluster and their ties, I analyzed the comments contempt (interaction, social ties and social capital) and afterwards, the cluster structure within time (dynamics). Well, there is a lot to talk about that but the conclusions were, basically: - it is possibile to find at least 2 types of clusters in fotologs: One is created through interaction between users and represent a type of community very close to sociological concepts of VC. Those usually have strong ties and also strong social capital within users. The second one is created through association and is not related to social interaction at all. - Most of the interaction-centered clusters are strongly related to geographic spaces and language; - Users recognize these nodes as their "group of friends" most of the time. So, I think virtual communities are a part of social networks as you said. But I also think there is a very important difference between the community (the users and their ties) and the space (or system) where they share these interactions. Orkut, for example, is *not* a virtual community but it can help people create one. Most of the "communities" in Orkut, for example, have no interaction between users at all, only spam. People join these communities as a statement (an addition to their profile, for example, to show likes and dislikes). So are those *real* communities? In my opinion, a VC is basically a group of people so, orkut communities may help them appear, but they are not a VC just because they exist. []s Raquel