I found this map after writing the social nets – virtual worlds come together post, which seems to endorse the thesis. It was on Personalize Media and I found it through Mike Butcher’s mbites. Apologies if the resolution is poor, I think it should be readable.
The more I think about this the more sure I am about it. In most ways Second Life is best understood as a social network, as are Habbo, Stardoll etc.
I’m not sure talking about web3.0 is helpful yet, but as Second Life explodes I can see people talking about second generation social networks before too much longer. According to their blog they have just passed 1,000,000 residents and are growing at 1-5% EVERY DAY.