<p>This is more a comment than an answer, but I don't want to promote the comment-answer trend (please note that I can understand why sometimes people leave comments rather than answer!).</p>

<p>IMO, 'useless answers' are not the way to go. Because we expect answers to be on the point and useful for future visitors. Rather, we can bounce those questions from time to time (editing, retagging, etc.), and wait for users' reaction. If nothing happens then it's just that the question does not deserve that much attention, or nobody is qualified to respond to it. So what? We should expect unanswer{ed|able} questions from time to time.</p>
