Just found out about a paper called Thoughts on the Social Graph that mirrors some of the discussion I had today in getting a Social Network built for the Web Analytics Association (under discussion right now - it falls under my committee - Social Media and Community which I'm the Director of). 

The issue of an Open ID came up over and over again in our discussions - and it's all over this paper - and it makes sense that inviting people to every social network is a replication of work that no one really wants to do.

But right now, there's still no easy way that's adopted by everyone to read in data, friendships, etc, from one social network into another - at least, not yet.  Read more in Thoughts on the Social Graph which I heard about from John Battelle's post on The Social Graph