That is the dream. One day I think we will get there, but its going to take people pushing the Facebooks and Twitters to embrace such a system. Facebook has been going the opposite direction with its API and has killed off a number of things making it harder and harder to interact with.
Maybe a two approach method could help advance this goal : 1 - having a bunch of alternative social network (GNUnet,Diaspora etc..) to adopt ...