Moderators are allowed to close questions that are blatantly off-topic, or blatant cases of questions for which a closing reason is valid.
Unfortunately, there isn't a way to avoid low quality questions are asked. Even if the FAQ clearly states which questions should be asked, and we have questions tagged faq that guide the users about how to write a question, there is always somebody who asks a question that the FAQ suggest not to ask.
I think the solution is educating the users, and (most importantly) the users who should close the questions, or flag them.
We should made clear that not every question asked from somebody, and which is someway related to Drupal is acceptable, and that a minimum effort is required from who asks the question. Subjective questions asking for the best module, or the best way to do something are not questions that help future reader. Questions asking how to implement a feature, but that doesn't show any code written by the OP show little effort from who asks the question; Drupal Answers is not the site to give fish to who needs it, but the site to teach users how to fish.
Users should understand that closing a question doesn't mean "you are not welcome to ask questions here"; they should understand the closure means "your current question is not acceptable, but if you change it to make it acceptable, then it can be re-opened."
It is also important to explain why the question is going to be closed, to avoid the users feel like their questions are closed because somebody didn't like them. Starting from today, I will add a comment explaining why the closed question is not a good suit for Drupal Answers, even if the question didn't get a closing vote from me. I hope more users will comment about the reason for closing the question too.
As side note, in the past 2 days, 16 questions have been closed; since the beginning of the year, 68 questions have been closed.
Between January 1, and January 8, we had a peak of 15 closed questions. Previously, the peak was of 17 questions closed, which was verified between October 8, and October 16.