There are almost 3900 unanswered question on our website. I have red this thread, and I want to add two categories of such questions. What I want to know is what we have to do with these questions.
For the second type of questions, especially those with no answers (which is slightly different from what the software calls unanswered), just vote them down. The system will automatically clean them up. (See this discussion here, where this MSO discussion is linked to.)
For the first type: I don't think it is really a problem. It may also give new users who wish to contribute by answering questions some low hanging fruits to attack first. Unless, of course, they are duplicates, in which case they should be closed as such.