In the beginning, RPG.SE was Community Wiki crazy. We used it for everything. We have an old Meta question on what to use CW for. But then we realized list questions were bad and CW was being used as a dumping ground for bad questions. So now CW is anathema. Some hunt down and kill old CW questions, annoying old users. But some cases have come up recently, I think, where we should consider what CW should be used for. So here's a new question to obsolete the old - what should we use CW for in 2012?
I think there are some exploratory "list" questions that are a good fit. There's "laundry" lists, which are just long lists of simple game names or whatever. Then there's design exploration questions like Brian's Useful mental frameworks during character creation seem like perfectly good content for the site. Design exploration falls under "by experts for experts," IMO. ENWorld is keeping a page like this (http://www.enworld.org/index.php?page=dnd5e) but that's not community contribution, it's curated by the ENWorld guy.
Edit: nowadays we've decided list questions are just off topic, instead. Same with "design exploration" that's not tightly scoped.
Also, I think we should consider a "D&D 5e; What we know so far" CW to prevent bad Q&A like Will a 5th edition of Dungeons & Dragons be released? and https://rpg.stackexchange.com/questions/11814/how-will-the-play-testing-for-dd-5th-edition-work from erupting, while still gathering useful info and driving people to the site. I think collecting info like this also counts as a good "by experts, for experts" use.
Edit: And in a separate newer question, we've decided not this either. Would Community Wiki be useful for questions about the “current” state of something?
What to NOT use it for - everything else. I think it should be a safety valve for things extremely useful for the site GOAL that don't quite fit the usual site FORMAT.