Live Forums?

I’ve been listening to Dan Benjamin and Marco Arment’s excellent podcast Build and Analyze, and they’ve been discussing the best ways for programmers to interact with eachother - or, more accurately, which methods stink. I thought about it yesterday too, and I think I have an idea for what would be awesomely useful: a live-updating forum, where every forum thread is basically a conversation while still retaining the organization and permanence and searchability that make them so useful.

The idea actually kinda reminds me of Google Wave, but it needs to be less private - everyone should be looking at the same page.

So, my question is, does this exist?