In terms of these sorts of developer oriented features, I'm much more excited to see Camlistore take off. Portable, better sync options, open source, support for any backend, etc. Just something to look at if this topic is interesting.

In fact, their semi-slogan is "your home directory for the web". Very privacy focused (an encryption layer for backends is in progress based on their issues log), since that seems to get buzz these days.

http://camlistore.org/