I'm also beginning to have a very strange thought that a reddit-derived blog system with comment upvoting and karma is just a vastly more effective way of researching decision-theory problems than publication in peer-reviewed journals.

How relevant is the voting, as opposed to just the back and forth?

I think the voting does send a strong signal to people to participate (there's a lot more participation here than at OB). If this is working better than mailing lists, it may be the karma, but it may also be that it can support more volume by making it easier to ignore threads.