It isn't an alternative to Facebook unless my grandma can use it, and she couldn't set this up for herself. The idea that centralized storage is the problem masks the actual concern. There is nothing inherently wrong with centrally stored data. There is a problem is when it is locked down by a 3rd party, and/or you don't control how it is used.
Actually with a few tweaks, this technology would be much simpler to use than Facebook, for a person like your grandma, simply because it removes that annoying registration process. You just open the installed app, and that's it. It's odd that we got used to the idea that "(1) registration, (2) strong password creation, (3) username selection (in case of conflicts), (4) email verification link, (5) login" is somehow…
Cycle.js and xstream are amazing, as an aside. Thank you.