Open Social - the Commons of Social Spaces

I just read an article talking about the collaborative efforts of Google and Yahoo to push forward the Open Social information standard. This will essentially create information portability amongst various social networks. In general I think it is a good thing provided that the public uses the technology. The real question becomes what is the differentiator amongst the sites? If the space allows information portability (think ell phone numbers) what is the reason to go to one network or the other and stay? Friends, Service, Layout, usability, features. Time will tell what is the real valuable piece of the social networks.