With the recent "Web2.0 Penetrating the Enterprise" bandwagon, I suspect we’ll start seeing much discussion on what qualifies for the category.
Companies like SelectMinds, or Ross Mayfield‘s SocialText have been long applying, successfully, many Web2.0 tenets in their enterprise work. What I am afraid of is the apparent need, in blogsphere, or the tech press, to create neat matrices and tables to try to categorize and impose a taxonomy to this phenomenon. See this chart (from Jim Cuene) to see what I mean.
Isn’t that exactly what we’ve learned not to attempt over the last couple of years?