Whenever a question is made community wiki after the fact, it seems like all the associated answers don't also get concerted. Here's an example:
2 Answers
This is by-design. Answers posted after a question is manually converted to community wiki will automatically be made community wiki. However, answers posted before a question is manually converted to community wiki are not switched over.
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$\begingroup$ This seems like not the best behavior when these questions clearly should have been CW to begin with? $\endgroup$– ShaneCommented Feb 13, 2011 at 15:08
We have provided some additional guidance at the blog:
http://blog.stackoverflow.com/2011/08/the-future-of-community-wiki/
TL;DR version
Most of the time, you should be asking yourself “How can I improve this post so that community wiki isn’t needed?” Community wiki is like a cheese knife: it is a specialized tool to be used sparingly, and only in very specific circumstances.