There have been some feature-requests over the years which have proposed slowing down the question-creation process for new users.
We could implement this idea of a "question wizard" in a way that, when you are a new user, it takes, say, 5 minutes to ask a question. Then, when you hit 50 reputation, a few of the steps are taken away, and it takes more like 2 minutes. Then, at 100 reputation to takes a minute, etc..
Obviously the rate at which the speedup occurs can easily be adjusted as the team tests the idea out.
This would encourage users to keep their accounts longer, since it takes soooooo loooooong to ask a questions as a new user. It would also have the byproduct of (theoretically) increasing first-question quality, as users would have to slow down a bit and really think about their question (well, really just wait impatiently while the timer ticks down, but one can hope...).
This, combined with the more aggressive rate-limiting mentioned in the comments, could make the number of new accounts created more manageable.