The big problem in the future will be the fact that as the line between "real" and "online" life diminishes, the party which holds the data will become an authority akin to governments we have today. When or why should we trust an authority? How can we be sure that the authority is trustworthy? Politics is hard enough and we all know that we can't trust politicians, how on earth are we going to trust a party with commercial interests to somehow manage our social lifes?
You seem very optimistic about things like Facebook collecting data and interlinking people's social life via their platform by using the collected data. I for one find this very scary, to such extent that I'll rather cripple my social life and not use Facebook than trust an commercial authority over the data collected about me which I have no control over.
I provide the data. I see the data. I own the data. I control the data. What is so hard about it? Honestly.
Also, not using facebook is difficult to imagine for me. It's pretty baked in to my life.
The thing is, Facebook could be better by allowing members to invite outside data to flow into their feeds from chosen sources, and providing more freedom with data-exchange in general. Enforced segregation is costly.