Google have canned it.
Had potential but invite only made it utterly useless for it's purpose, lack of news about it or connection existing services such as gmail meant it hardly ever got visited, and people who just want stuff to work scratched their head and asked what the hell it does and how do you use it.
Oh and it apparently ran like shit, but I don't know from direct experience, - why would I bother with it when I have like, 2 friends on it (who didn't use it either for the same reason)
Great ideas, piss-poor execution. Perhaps some of it's technology should be integrated with gmail and google's upcoming social networking thingy.