But SMTP is still a distributed protocol, you can switch providers in a blink and not lose anything other than a shiny interface.I think you may underestimate the importance of the shiny interface. Regardless, the use of an outside provider is still a move toward centralization. Ten years ago, the small offices I did software work in all had local email servers. Today, running an email server well is a big job, and those offices all outsource their email service to much larger companies.
People ... demand the "follow individual" pattern (RSS) ... In the future some smart kid will come up with a "DNS for social relations"
It's interesting that you bring up RSS. I was thinking about that too. I think RSS is already very nearly a "DNS for social relations." But it's also failed to catch on outside the circle of techies, early adopters, and web-potatoes.
I'd say the failure of RSS to achieve mainstream popularity is an example of a decentralized system losing out to centralized alternatives. Like Facebook. Facebook is just plain simpler to get started with than a self-administered approach like RSS or a hypothetical next-generation DNSfSR would be. And Facebook and Twitter both killed off their RSS feeds once they'd felt they'd achieved a certain critical mass. They understand that RSS is an alternative for much of what they do.
I don't celebrate any of this. I use and like RSS. I wish I didn't feel the need for a Facebook account (but that's where my real-world friends are). But the pattern I see is that convenience beats out control every time. For complicated devices like computers and for complicated situations like the (real, human) social network, the inevitable complexity that comes along with local, personal control is often a problem, not a feature.
Under such circumstances, I don't see how Facebook (or its successor) will be overtaken by a distributed anything.