I have noticed that a sizable fraction of posts tagged both [big-list] and [soft question] on this site have over ten upvotes. Moreover, another sizable fraction of those were posted by users under 500 rep and started off as non-community wiki. It seems possible that some of these questions are posted purely for the reputation, and frankly, I'm surprised that there aren't more of these posts. While there is nothing inherently wrong with that, a lot of these users have gained a large amount, if not a majority, of their reputation from that single post. Here's my suggestion: questions with both of these tags and more than a certain number of upvotes should automatically be made community wiki. For the number of upvotes, I would suggest ten. I have three reasons for this number. First, I think that new users can crave reputation for legitimate reasons, such as getting more privileges, and for new users, 50 reputation seems like a reasonable value from these questions. Second, these questions are important contributions to the community, so I think some reputation gain is certainly deserved. However, any more reputation gain would mean that people could just start churning out these questions and get excess undeserved reputation.
P.S. Please forgive me if I'm being hypocritical.