I know 3 completely separate (and non-tech focused) groups of people (each 30+) that were/are running on Wave and are each pretty upset that its going away. I know that each of them came to swear by Wave for almost all intra-team communication.

It wouldnt be a stretch for active users to run into the high tens of thousands. Unfortunately, thats tiny compared to the usage of Google's high-profile projects, so it gets killed.

If you want a conversation between more than two people, Wave kicks everything's ass. And unless you're the kind of group that's comfortable with setting yourself up a phpBB, I can't even think of anything that comes close.

Wave's problem wasn't that it's not useful, it's that nobody knew about it (of people I know, it had 0 adoption outside of computer geeks), and it couldn't integrate with desktop applications. A lot of us are stubbornly hanging on to Mail.app and Entourage because they integrate with our workflow better than web based solutions.

If google had come out with a a desktop Wave client that worked with OSX's address book, photo libraries, etc, it would have had a lot more draw. That sort of integration is less expected on Windows, but I'm sure they could have come up with some compelling features that the website didn't offer.

I completely agree. I know from my experience that if I could have just put in my normal Google Apps email and pushed everything through Wave, I would never look back. The fact that it was a self-contained, closed system killed a lot of its usefulness.

The technology behind it seems to have made it into Google Docs (real time collaborative editing). There are plenty of people using Google Docs.