It used to cost the person who down voted a question 1 fake internet point. It was determined that this was sufficient to stop people from down voting questions that really needed it so for questions, it's now free to down vote. 

The only guidance available for down voting is in the tooltip 

> This question does not show any research effort; it is unclear or not useful.

What you see is community members exercising their privilege, using the tools they have available, to try to enforce quality. Quality is a real issue on Server Fault, we need so much more of it.

>every question deserves an answer, even the dull ones.

92% of all questions on SF have a written answer and pretty much all questions get answers even if the answer is your '_question is not a good fit_' or '_is so poorly written/presented/vague as to be unanswerable_'.