Edit: there's been some discussion on the issue of genre being murky. This is a great point and more discussion is welcome.

I haven't seen this touched on yet, so I thought I'd throw this idea around. For those who aren't already familiar with this, tags are added to threads by the OP (a maximum of two). However, a third tag is also able to be appended as voted on by the community. If you view the tutorial (see the bottom very of any page), it touches on this a bit. thenewgreen has written about how exactly this works in this thread. It reads as follows.

To answer your question.... Next to your name in the upper left hand corner is a "hub-wheel". This wheel populates more and more as you use the site and are recognized. Once you've completed a full wheel you will be able to administer "community tags". For any other questions check out the FAQ page, the "ABOUT" page and the "TUTORIAL" at the bottom of the page. Beyond that, feel free to let me know if I can answer any questions. Thanks and welcome!

So, perhaps that could be something to be looked at as a partial solution to the problem of genre tagging!