Social network. Simple. At least until someone has to justify their job by coming up with a new name for it. I got momentarily confused recently when all this talk about Social Graphs started spinning around until I took a breath and looked at it.and realized it was just another way for saying Social Network.
Dave Winer penned an interesting post on the topic that sums up my feelings on this exactly. The title says it all: How to avoid sounding like a monkey. Should be a lesson to some primate out there somewhere.