Couldn't agree more. The system they cook up will be one of many websocket wielding filesharing services. What will they do for browsers without websockets, flash supports sockets (cofounder Tyler hacked out a quick fallback).
Maybe it's better to just not suppor older browsers?
My guess is that people who are interested in Diaspora, at least at first, are current on their web browsers. I think there's a trend among web services (esp. Google) to prod even everyday people away from older browsers, especially IE6.
Then again, if they want widespread adoption, they can't just support HTML5-compliant browsers. Hmm...
Maybe it's better to just not suppor older browsers?