Highly recommend this post by Marc Canter, it's filled with ideas. Much the same as my thinking. I have a post planned for tomorrow or Sunday that should blow out some assumptions about identity and federating these micro-blogging services. Low-tech, worse is better, re-use what's already out there, as Marc says it's all happening now, and I'm loving the way it's turning out.
Recent stories:
Dave Winer, 53, pioneered the development of weblogs, syndication (RSS), podcasting, outlining, and web content management software; former contributing editor at Wired Magazine, research fellow at Harvard Law School, entrepreneur, and investor in web media companies. A native New Yorker, he received a Master's in Computer Science from the University of Wisconsin, a Bachelor's in Mathematics from Tulane University and currently lives in Berkeley, California.
"RSS was born in 1997 out of the confluence of Dave Winer's 'Really Simple Syndication' technology, used to push out blog updates, and Netscape's 'Rich Site Summary', which allowed users to create custom Netscape home pages with regularly updated data flows." - Tim O'Reilly.