I haven't done any research, so maybe it is out there.  But I had a thought the other day as I accepted yet another invite to connect from yet another social networking site from someone I have connected with numerous times. 

Wouldn't it be great if I could have one, unified set of social contacts, my social network, that I could then just share out to various social networking sites?  I mean, sure, folks would have to opt into it, someone would have to think about the privacy issues, but good grief, it seems like we need something like that...