Twister
From Just Solve the File Format Problem
Twister (the open-source system, not the "right-foot-blue, left-hand-red" game or the storm that blew Dorothy's house to Oz) is an open-source, encrypted, decentralized implementation of a networking service similar to Twitter. It is implemented using protocols similar to those used by Bitcoin, with the "mining" procedure used to validate chains of activity that verify who registered each "handle" first to avoid name conflicts. Instead of "coins", the "miners" are rewarded with the opportunity to send "promoted messages" to participants.
Twister also uses elements derived from BitTorrent, and uses JSON for API interfacing.