In case you haven't seen it, consider reading Michael Arrington's TechCrunch post calling for a decentralized Twitter. (http://www.techcrunch.com/2008/05/05/twitter-can-be-liberated-heres-how/) As noted by many of the commenters, and as should be obvious to anyone in the Jabber community, the solution they are looking for is probably XMPP + XEP-0060 + "Atom over XMPP".
bob wyman "Atom over XMPP" is defined at: http://www.xmpp.org/internet-drafts/draft-saintandre-atompub-notify-06.html
