I tried to propose an idea where I work of having a threaded chat room to mimic conversations in the hall. It could get even better by having some intelligent gleaning of conversation keywords and showing those visibly by each chat room, so people know when their ears should be tingling and can join in on the conversation.

The method of a single chat room means multiple crossing conversations become hard and there's constant distraction trying to see what people are talking about only to find it's not interesting to you.