There are some questions on SO that no one really can solve, since it is missing information. It's not bad questions, it's just that it needs more info. There are comments to add more information, but the OP doesn't respond to it.
These questions just hang around in the unanswered queue never to be answered I guess..
One example is this. It was asked in February, but the OP never got around to respond to the only comment he received. At the moment this question will never be answered..
Should I as a user flag these questions to a moderator? Should we wait around and see if the OP gets back? Should I add a second comment? upvote the current comment?