I made this answer community wiki because I only posted an extremely partial answer. Since the content seemed to be useful and too long for comments, posting it as an answer seemed somewhat appropriate, but the answer certainly required extra work. (This use of community wiki seems to fit with what is stated briefly in this blog post: 'An incomplete “seed” answer is a stepping stone to a complete solution with help from others'.)
This brings up the question of when a poster should mark an answer as community wiki.
For FAQ-like questions on Meta (especially those that generate short list answers for which elements in the list are not disputable), marking an answer community wiki might be reasonable.
A similar argument might be made for a question on the Main site to allow a single answer to better address the complex question. However, expecting others to sacrifice potential reputation gain by adding to a community wiki answer (rather than posting a less complete answer) may be somewhat unreasonable. (On the other hand, such would allow a user to add a very small amount of content which would gain little or even negative reputation if posted as a separate answer.)
So the question remains: When should an answer be made community wiki?