One of the major reasons that DNS is so successful, and that OpenID seems to be catching on, is that they allow any person to set up a server. Each client decides which servers to trust, but servers can be set up by anyone at all. It seems to me that it will prove difficult (not impossible, but difficult) to make social graph data portable, so long as each company develops their own tools to provide an API to their data. Even if most companies adopted FOAF as a standard for exporting their social graph data, any new companies would need to develop new libraries to import, export, and use that data. I believe that a distributed social graph server, a-la OpenID, that served up its data as FOAF, could provide a nonpartisan solution that would be adopted very quickly.