Some people tend to post what genre their post is, some don't. Personally, I like seeing the tags there so we know what we're about to listen to, or at least get an idea of it.
Probably wouldn't be a hard rule, but maybe something added to the sidebar like "Please add a genre description. if you remember to."
Whatcha all think?
EDIT: For clarity, all I mean is formatting post titles like "Weedeater - Wizard Fight [sludge/punk]"
Genres are big circles on a giant never-ending Venn diagram of types of [thing in question]. Multiple genre labels will often apply to a single piece of music, and you can trace the influences that led to a certain genre's emergence.
Don't think of it as categories in the music store. Think of it as a taxonomy that primarily exists to help you find stuff that's similar to what you already like.