Blogs are all about talking, but they're rarely about conversing. They're more like monologues within earshot of one-another, and sometimes another person will tune in and change their own monologue in response. Twitter's basically the same thing, which isn't too surprising since it's really a form of blogging.
I wonder, though, if there's a way to invert the pattern. Instead of everyone talking and hoping someone listens, is there a way you could reverse it so there's much more listening going on than talking? What would such a thing look like? And would people use it?