Diaspora on Open Source Rails

Distributed Unlike centralized social networks (eg, Facebook), Diaspora has no central system that owns all user data

Unlike centralized social networks (eg, Facebook), Diaspora has no central system that owns all user data. Distributed pods act as web servers, and connect to other pods, forming a connected social network. Self host: host a pod yourself and connect to the Diaspora network without registering on anyone else’s server. No lock-in: migrate pods or export all of your user data.

Full article: http://www.opensourcerails.com/diaspora/