I sometimes find myself wanting to play something, and go browsing the site in order to find such a something. Often enough in these cases, what I want to play doesn't fit easily into the tags or genres available, or falls under particularly broad tags or genres.

However, even in these cases I can often easily-enough identify what I don't want.

Thus my suggestion: that in addition to the current functionality of selecting tags or genres that are to be required in a search, functionality be added to allow the selection of tags or genres to be excluded from a search.