Lately, I've been losing enthusiasm for this site, so I don't bother answering questions if I don't think I'm going to get any gratitude (in the form of an upvote, an accept, a "thank you", or some indication that my work has some value to someone other than me). So, before answering, I check to see if the questioner has asked questions before, and, if so, whether he or she has ever accepted any of the answers. For ingrates, I'm much less likely to provide an answer. I would guess that other people do this, too.
Would it be possible to provide an easier way to do this check? Perhaps there could be an easily visible "ingrate" or "hard to please" badge awarded to people who persistently refuse to upvote or accept answers, or something like that.
Another benefit is that questioners who see that they have received this badge might be prodded into taking some action.