A few minutes ago I saw a question with at least two standard answers, I mean, plain answers to the question, without warnings/cautions/etc. The weird thing (at least to me) is that such question had not (up)votes!.
My etiquette and/or common sense dictates me that if I am answering a question is because I consider such question minimally "worthy", so I upvote the question. When I don't consider the question "interesting" I simply close it (the browser tab, not the question!), even when I am able to give an answer.
Summarizing, I think that it is "morally mandatory" to upvote any question to which you are providing a "normal" answer, but I would like to know the point of view of other people about that.
Edit: English is not my cradle tongue. "morally mandatory" was a very improvised and unfortunate choice of words. After some hours of thoughts (and digging in some online English dictionaries ;-) ) I can honestly say that the word that reflects more accurately my feelings about this matter is "consistent" instead to that dogmatic term "morally mandatory".