I think people are thinking to small. Imagine if you could own your data profile and "invest" it into websites or services. Everyone builds their services to accept this same "profile" formatting and the user takes it where they pleases.
This would mean small upstarts can compete with google and Facebook (who right now have a huge head start on having all this data) by having a better UX.
right now, everything is trapped in all these different walled gardens. I see it like your cellphone only being able to call cell phones of the exact make and model of your own.