The below is no longer relevant since posts are no longer converted automatically to Community Wiki after being edited
As the Community Wiki process can't be undone and is automatically happening after five people edit the same post, it will be good and essential idea to add warning: "Your edit will make the post Community Wiki, sure to continue?" or something along those lines.
Just happened to me (was the 5th to edit a question) and I never intended to make it a wiki. Yes I know, will check how many people edit it before but it was new question so never assumed four people edited it already. :/
Edit: as "compromise", it will also be really cool to have count of how many people already edited the question, this way if I'll see "edited by 4 people" I will think twice if my edit is really necessary.
Edit II: I was under the impression that having the "root" question become CW all answers also become CW as result and no reputation is gained - however I've just noticed that impression was wrong and the answers are safe and sound.... so this is really just to prevent situation where one action (editing a post) is triggering other action that is not trivially related (making it Community Wiki) without any warning, especially when that unintended action is not reversible.