If memory serves correct, Yahoo! made a big push a few years ago to get people to "petition" their app security geeks to allow them to have IM, and that, I believe, fell flat. Somehow, in the corporate world, good intentions for software on an enterprise scale have a bit of trouble getting to the right decision makers. I think Google's future plans (Web OS & office suite) might not get too far past the "bee-ta" stage.

Incidentally, I was on the team evaluating IM for my company, and only one other person on the team was an active IM user. Aside from ease of implementation and features, the one most important thing they were looking for was control of the interface and access to everything everyone was writing. Do you think Google's going to give the corporate app spooks and auditors full access?