I think they're useful, but people keep making new ones up. Braindance considers themselves progressive darkwave, but they're really just doom. I really don't get why they make up new ones; if people don't know what their "genre" means they are less likely to check them out. I think we should just stick with the major ones, and bands that fit into two should be noted that way, like technical death, or progressive thrash, etc. Speed is thrash, grindcore is death, viking is black, etc. Sure, they are slightly different, but the basic sound is the same. That's what I do, and I think it'd be less confusing if everyone else did, too.