In a way, a wiki is simply a scaled down content management system. It focuses on making authoring easy, partly by avoiding features such as an advanced workflow engine, complex permission management, hierarchical organization systems, metadata management, and so on.
Given that the main advantage of a wiki is the simplicity of collaborative authoring, it should be quite easy to make efficient use of wikis within an enterprise. Just ask yourself - what content do you need and want as many as possible to contribute to when we produce and maintain it?
Why not take a look at your intranet? If you look around a bit, some of the content on the intranet is probably not updated, incomplete or incorrect just because it is hard for the right people to easily update it. Valuable content might even be completely missing on the intranet for this reason. It has certainly been true for the intranets I have used.
One of the biggest obstacles of making authoring easy on an intranet is probably not the usability of the user interface, but the way users are given access to the authoring tools. The access to the content in the administration tool where you maintain the content and structure of the intranet is typically restricted to certain users with specific predefined roles that have been assigned specific predefined rights (on specific content types and/or groups of content). So, it is typically quite a cumbersome procedure to set up rights for users who only want or need to contribute on a small scale and probably something that has to be done my a user with administrator rights (and skills). At least it cannot be done the same minute that a user finds out that he or she can contribute with something of value.
An enterprise wiki on the other hand is (and should be) accessible for any user within the enterprise. When someone finds that something is missing, incorrect, inaccurate or incomplete - he or she can update the wiki in a split second.