The recommended Wiki (Confluence by Atlassian in this case), allows for Wikis within a Wiki (Spaces) so that multiple entities such as teams, departments or organizations can be served within one Wiki with collaboration amongst the entities still possible.
Read the complete blog entry at Transforming Business Weblog: Benefits of Wikis. The full blog, in fact, contains a good summary of wiki benefits especially as they relate to authoring in a distributed content management environment.
