Stack Overflow has got an interesting feature that may be related.
I can't tell that it helps to lower amount of bad questions asked (I honestly don't know if this is possible at all) - but it at least helps to save site home page from being polluted by such questions (bold font in below quote is mine):
All questions flagged Very Low Quality now immediately enter Triage
...and while these questions are being triaged, they're not shown on the home page. Take that, wall of crap.
See also:
- MSE discussion of instilling above features network wide:
Triage and Help & Improvement review queues at sites other than Stack Overflow?Triage and Help & Improvement review queues at sites other than Stack Overflow?