I'm not even sure whether "cloud-based group discussion threading service" is a correct description or does Knotable justice, as it seems to be quite a bit more than just that, but I find it hard to describe.
It might be a sort of fork of Google's Wave, I don't know.
Anyway, if anyone is interested in using knotable to find out what it is and what it might be able to do for them, head on over to http://alpha.knotable.com/login/
and register for an account. It's in ß testing at present, and FREE, though I am unsure whether it will stay free. There is also a blog at http://blog.knotable.com
They seem keen to have people join them for beta testing, though they haven't opened the floodgates to all comers yet. I was an early applicant for an account, but it was a few weeks before they let me in.
If you PM me in DCF with your moniker, once you are registered in knotable, I shall respond and commence chatting with you in knotable.