After some discussion about downvoting questions, my conclusion is that even though downvoting questions may serve a purpose, I believe it is currently psychologically harmful for the OP because he misinterprets the meaning of the downvotes. The correct interpretation is: "a member thinks that the question is unclear, does not show research effort, or is not useful for future users". But this information is nowhere written on the about page or FAQ.
The about page does not even mention voting up or down questions.
The FAQ extensively discusses what are off-topic questions, but does not describe what is a bad question (on-topic). It merely gives advice about how to ask a good question, but never specifies you will be downvoted if you do not follow the advice. Specifically, I haven't found a section explaining In which case should I downvote a question? (for voters), and What does it mean when someone downvotes my question? What should I do about it? (for the OP).
The only information about this is on the tooltip that appears when you mouse-hover the down arrow before downvoting, that I don't expect new users to read, and is anyway not very explicative not knowing the SO culture.
Hence, when downvoted, a new user have to guess what this downvote means, and I believe the first guess is to feel insulted, and insulting is of course against the policy of SO (it doesn't really matter if the downvoter didn't mean it that way, it is still the way it is perceived).
Then I would suggest making the correct meaning of downvoting questions clear in the about page, or at the very least in a FAQ section "What does it mean when someone downvotes my question? What should I do about it?" that we can link when downvoting, or even better, that is automatically displayed to the OP when a user downvotes the question.
It's something I'd been thinking about posting as a proposed FAQ for a while