I've been running a buddycloud server for the last few months, and I think it's a great project. I particularly like the way they have re-thought social networking from the start, rather than just blindly copying facebook / Google + etc.

I think that for opensouce projects to have traction, reinventing a closed system isn't going to win over more than 1% of potential users. A federated social network also changes many of the social networking paridyms - like how you trust other domains.