'Life on the Move': Social network sites and online communities

I would like to join Daniel Skog(here) in advertising our roundtable discussion at this years IR 9.0 conference in Copenhagen. We have a great collection of people coming together to discuss the tribulations involved with studing 'community' now that SNSs are dominating the online social landscape. Here is an extract from the roundtable description:

Social network sites (SNSs) like Facebook, Bebo and MySpace are rapidly becoming a popular area of research investigating online 'communities'. This immediately raises the question of how new SNSs can be understood as a descendent of the 'virtual community' that was popularized in the 1980's (Rheingold, 1993). One irrefutable piece of information is that the number of users that seem to be joining these new sites has been growing substantially over the last few years (i.e. comScore reported Facebook had an increase of 270% between June 2006 and June 2007). This could indicate that SNSs has become an integral part of everyday online activity as a whole. The purpose of this roundtable is to further discussions on the present shapes of online communities in light of the current trajectory of social network popularity. In particular, to what extent are online communities tied to a particular site? And consequently, how can we rethink notions of community in line with recent trends in SNSs?

[...] The underlying premise is that 'life on the move' produces a certain problem for academic researchers as to how we locate the individual (or the community) in such a dispersed social landscape. Therefore, how can we understand community involvement when users are members of a number of different community sites and SNSs and move regularly from one site to another? A further problem here is how we as researchers resist the mundane assumption that inherently complex online communities are only recognisable in terms of the users movement in and out of them, surely there is much more to it than that.