Perhaps a "social graph" shouldn't belong to any company. The concept itself might be anti-privacy.
Perhaps it's time to move back to simpler things like OPML. (Which people seem more comfortable sharing freely - not sure if that's still a "social graph" tho.)
Perhaps specific relationship details shouldn't be housed in the social network - just the permission to follow.
Perhaps companies who house a "social graph" should be regulated - similar to what is done with medical data. It should be a toxic substance.
I just think we're a long way from doing this right and there are a lot of untried options - and I lack imagination as well.