Instant Messaging, Discussion Boards and Somewhere in Between

Andy and I were talking the other day about the limitations of Instant Messaging - mainly that you can't go too far in-depth in a discussion because it would take too long to type and you have people waiting for you in a real-time environment.
I told him that I had been thinking the other day that it would be interesting to have something in between IM and discussion boards. Basically, it would be real-time, but would be a threaded discussion, so that if a group was talking about more than one topic, or had more than one question that was being asked, members could create new threads. In that way members wouldn't be jumping on each other's answers constantly or waiting for others to reply.

I envisioned it like hypertext or hypercard. What I mean is, I envisioned boxes linked hierarchically according to topic/question. When someone posted to one of the links, it would flash on and off, so that members would know where to look.

I'm not sure that this tool woould be effective, particulalry in a small group, since we might be jumping all over the place to get to each other's ideas/questions (read: cognitive overload). But perhaps a larger group would find it beneficial.
Then again, maybe not.