I'm almost inclined to think that we should just close/delete old (at least a year) questions that have no upvoted answers or no accepted answer (i.e., the tumbleweed questions). As @voretraq7 points out a majority of those questions are created by hit-and-run users. They'll never come back to update their question, answer any of the comments asking for more information or to answer it themselves. These questions just seem to languish and even if they are answered, the poster will rarely return to mark the correct answer. There also seems little incentive for users to try to answer these questions as the poster will likely never upvote or mark their answer as correct. Additionally, the SF Community will often ignore the answers as well (just look at how few Revival and Necromancer badges are earned).
Active participation is crucial to keeping the quality of the content on Server Fault up and I just don't see how we can do that we these kinds of questions. We need good questions with good answers. Just having a collection of good questions isn't that useful.