There is a huge anti-revolution going on the last years. It's the "Web 2.0 isn't for serious people" attitude. Followers of this thesis will point out how digg doesn't present business-relevant news, and many famous and popular 2.0 services aren't usefull anyhow in a working environment. These are often strong arguments (take a look at the front page of digg and you will see what I mean) but let's see it from another perspective.
Think about YOUR intranet: it might be featureful, it might support document management integration and have many many features. So, what is missing?
Community, that's what Web 2.0 is all about. It doesn't matter what you are doing with it, but you need a community nowadays.
Now imagine an Intranet where you can know who's online looking at their faces in the upper part of the page, and you can chat with them with one click. Think of a Tag-based information repository, a user-based internal news system and personal blogs. Then, think about integration with outside services, and maybe even your partners' extranets.
If you still don't see how this can help the business, review the budget for the HR division under the "team building" entry: you'll see it can cover twice the price of such an infrastructure. Decrease in productivity and work time? Think about cross selling, think what your organization can do if it really starts working as one individual.
Maybe web 2.0 as-is isn't business oriented, but the right ideas are there for you to take. Do not overlook them.