The only timeonly time I've ever used the community wiki feature was when the answer was a snapshot in time. As a general rule topics that can only be answered transiently are not a good fit for Stack Exchange sites, but there is the occasional exception.
I tend to agree with Womble that there are few scenarios where it's worth using the feature, especially if you're a low rep user who could benefit from additional site access. The 500+ Fake Internet Points forfeited in the above example don't mean much to established users on this site, but would definitely have been useful to others.
In practice, most of a community's wiki-like content ends up on the Meta site anyway. A good example of this is our Canonical Answers page.