It'll be interesting to see how much abuse (at least attempted) is a factor.
Now anyone with a valid Live Id or hotmail account can contribute content directly to the main msdn web site.
Although the wiki feature is currently available on only the VS2005 and Windows SDK managed reference docs, over the next few months it should grow to encompass most if not all of the content in the library.
A few features:
Inline editing and history viewer
Add/Edit from within the Visual Studio ide
Wiki content is discoverable via online search engines