I thought the point of a Community Wiki was so that multiple users could edit one answer, and have lists generated and consolidated into one entry.
Why is it then, that we commonly see Community Wiki posts with multiple answers? Is this something that should be corrected when it is seen? For an example, refer to the CW made for RPG Terminology. There are currently two answers which are meant to serve the same purpose, where there should be one answer that has the contents of the two combined.
If the list has an implicit request for quality ranking between the answers or a grading of the answers, the different items should each be their own answer and voted on separately. Such as resources for specific purposes. (Since the changes in the usage of CW posts, though, this type of question would probably be asked as a normal question and switch over to wiki if it was requested or when it hit >30 answers, assuming it wasn't closed first.)
If the list is a collection of facts, particularly facts that have an order(i.e. alphabetized or chronological), it should be in one answer so that order can be maintained. For example the badge descriptions and recent feature changes wikis on MSO. They will split out to sub-answers as the text gets too long for a single post, such as when the badges post was split into A-L and M-Z. Then links to each sub-answer can be added to the question body.
I'd say that the terminology wiki probably should have one answer which is alphabetized. Though, we could have one answer for generic terminology and a separate answer for acronyms and then split out a separate answer for each of the the major systems (D&D specific terms, GURPS, etc.) into their own answers. (See the other answers in the badge descriptions: badge families and tag badges.)
Also, I'd think we want to keep the definitions as short as possible, leaving the long winded expositions to other sites which we could link to for further information. (i.e. this is not an encyclopedic entry with a complete historical definition and etymology, it's a here's enough so you can at least understand the answer to your question kind of entry.)
Well, it is possible for a single answer to be community wiki when a user wants to invite others to edit it -- it doesn't have to be a single question / single answer model.
However, in the specific case you cited, it does seem silly to have two answers when there should be one, so maybe flag it for mod attention with the rationale.
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.
We could adopt the Quora pattern for questions with lists - there is a "Summary" answer that cleans up the results, while leaving the individual answer-posts intact (for attribution, discussion, etc.)
That does require us to up-vote the summary - so an alternative would be to edit the question itself to contain the summary.
If the entire purpose of the question is to create a list, it is better to post the entries as separate answers. That way each individual contribution can be vetted (voted, so the 'more popular' answers rise to the top) and commented on.
But, in theory, you are correct; Wiki was designed to collaborate on a post by multiple contributors. If you consider the entire collection of answers as, effectively, the whole answer… you achieve the same purpose, with added benefits.
