I'm trying out Google's Buzz and I'm pretty impressed with this new democratic direction of social networking. Rather than having a single site which owns all of your data, Buzz aggrigates data from XML feeds on your various profile pages and then shares it with your friends. To prove I own a site, I just link with a "rel=me" tag from each profile to another profile, which at some point is linked back to my main profile proving that the feed belongs to me.
This is incredibly cool, but can only work if provider sites allow users to link back to at least one other profile with an XFN rel=me link. I think that this is in Microsoft's interest in the long run, they don't control any major social network and could easily emulate Google by doing the same thing in the future.
So, can I have rel=me to gaz.bitplane.net on my Photosynth profile page please? :)