It looks like social networking sites are the new in things on the net. Lately I got invitations to Orkut and OpenBC. While browsing at Orkut, i found lots of people that are not only attached to one networking site, but to many of them.
I think that those networks can be very additive - especially when they allow to rank others and to be ranked, when they show how popular one is etc.
I really wonder when those communities start their business plans. OpenBC as an example first offeres their commerical premium services. When after a month you are accustomed to all the features, the account falls back to the normal version and you have to pay to get the level of service that you know.
And by the way: the grandmom of those sites, Sixdegrees is currently down for relaunch.