Gartner has issued an interesting report suggesting that enterprises shouldn't ignore Web 2.0. It's tempting to see the whole 2.0 phenomenon as having to do exclusively with consumers and, after all, how many corporations need a means for sharing stupid videos? But the bigger issue is, how many corporations need to stay on top of consumer trends that employees will bring into the corporate environment whether IT likes it or not?
The first instance of this phenomenon was the "PC invasion" of the 1980s. At that time, IT groups lost a lot of power, which they only regained when employees realized IT could enhance the usefulness of the PC -- by networking, for example.
A more recent instance is IM. Many employees see IM as a huge productivity booster, but there is one significant problem for users: The major providers are incompatible with one another. Fixes to this incompatibility problem that only an IT department can provide are on the way.
IM isn't considered part of Web 2.0, but wikis certainly are, and the same pattern exists. Employees are rushing in whether IT likes it or not, but IT can provide a better solution, by enabling needed controls (such as the ability to restrict access), thus turning wikis into a viable alternative to enterprise content management systems.