Sococo has been around forever and always gets a major eye-roll from the HN community whenever mentioned in a thread.

But I don't think I know a single engineer that has actually used it.

I like the idea of seeing who is chatting with who. If I'm working on something, and I have two colleagues that are also working on the same project and I can virtually see them chatting, I'd probably approach to see if there's anything I know or if they're discussing ideas.