Forums, Google groups, etc, don't have the "edit other people's posts" Etherpad-like collaborative editing. Most of them aren't branchable in the same way Wave is. They generally don't have the privacy controls of a Wave. They don't weave from email-like to IM-like like Wave can. They're not built to allow native clients to interact. And they don't have any federation ability.

You could say that Wave is a bit like Email, Basecamp, Campfire, Etherpad, and a bunch of other collaboration tools, all merged into one unified interface. I'd be scared if I was 37-Signals. From everything I've heard, the feature Basecamp users most like is the discussion system... with Wave, that becomes a lot less worth paying for.

I haven't bought into Wave yet, although it has more to do with the current UI than anything else. In addition to what's mentioned above, there are plugins for LaTeX, for rendering molecules, etc which make collaborative editing very powerful, potentially at least.

Have you ever tried to use forums or Google Groups in a Fortune 500 company? Plenty of office workers have trouble with basic email. Getting them to use a forum or Google Groups is a lot of work for an IT staff. This is why you have products from Microsoft like SharePoint.

Google Wave is, IMHO, a godsend to corporate IT staff. It's a single application that solves several, very real office collaboration problems. Moreover, you can (or soon will) deploy it in-house, so you don't have to worry about a third-party hosted solution.

As far as I'm concerned, Google Wave solves all the problems of "intranets" and with a few robots and extensions makes a pretty decent project management tool too.

I hadn't heard this, yet. It will be deployable/hostable locally/privately? I see this as a big obstacle to corporate use.

It's an open protocol, and part of Google's stack will be released open source. So yes, eventually you'll be able to set up a private behind-the-firewall wave server and federate with the private behind-the-firewall servers at other companies (presumably including a robust email-to-wave bridge).

A forum doesn't pop in your mailbox, I would say, simply? And it's not personal, it's public.

You can tell google groups to send emails. Not sure if you can set them to private. Obviously you can do a private install of a forum and restrict access.

You can make as private as you want, but if a message is only for a part of the team, or only like two people, a forum doesn't help.

You can usually make certain forum threads that have specific member lists, granted it's not as 'ad-hoc', but it'd be reasonably easy to add the features to a forum.