P2P twitter is absolutely necessary but it has to be done right.

First of all, ensure privacy with public key cryptography. Sign tweets for authenticity. Retweets can just be additional signatures.

If a distributed microblogging protocol was interoperable with twitter and user friendly, it would probably be able to siphon people off of twitter proper. Certainly it would be an attractive alternative to anyone who NEEDED the service, and that's the important thing, right? Hopefully work out a way so that tweets on twitter.com can be captured and distributed in this P2P network. These tweets could be unsigned since if you include a link to the original tweet they can be verified.

Defining protocols instead of providing services democratizes a layer of the OSI model. We need to think deeper than that, though. We need to democratize the physical layer as well. Luckily we've proven that you don't need a high bandwidth link to be useful in a crisis situation. Twitter will do. To that end, I suggest that this project make an even more lofty goal:

Create a small embedded device interoperable with this P2P microblogging network. The device can communicate with peers over a Software Defined Radio. The device should be capable of bridging to a wi-fi or 3g network. This would accomplish the democratization of the physical layer which is so important to combat censorship and oppression.

You can't monetize democracy. This is why these projects will only happen on a volunteer/charity basis.