I think the concept is fine, but it needs a makeover. My suggestions:
1) One question per day, per hubber. To add some depth and to prevent automated spam.
2) Allow questions from hubbers who have an author score over 75. I know it sounds discriminatory, but a couple of good hubs make it easy to reach it.
3) Allow users to rate the question itself, a negative rating would autoflag the hub or possibly remove it, again only 75+ hubbers could rate and vote. It should help moderation stress noticeably.