I've had recently an idea (inspired by society outcry after the ACTA was signed by our goverment, but not only) I want to share. It might not be particularly original at a glance, but I find its details pretty exciting.
Abstract: Distributed and totally decentralized message passing system which automatically (protocol level) promotes popular messages ('I like it/Dislike it/Tell a friend' - type), and drops less popular with time. It includes all features found in other known solutions (like following someone, responding, thread talk, #hashtags, extensive searching) + ensures authorship with ECC signatures and grants certain level of anonimity to users who require it. By default, passed messages are public, but @ they can also be encrypted, also it should not be possible to post files (but see the spec). Message length is limited by the UDP packet size/ethernet MTU, but it can reach over 500 bytes (this paragraph up to the @ character).
Ah, and I've called it Weespur (pronounced: whisper) from the name of the passed messages - whispers.
Preliminary "specification" (or rather personal brainstorm file) can be seen in three formats exported from org-mode (I prefer the first file myself, suit your taste. :P):
Weespur specification / emacs html
Weespur specification / exported html
Weespur specification / ascii
Personally I would implement it (if at all) using Python and Xapian as a search engine/DB. If anyone is willing to participate - give me a heads up.