Hmm, I can buy the argument on principle, but I can’t think of a good implementation that wouldn’t be a ton of work to create and maintain. My library is only 400 albums or so by 70 musicians, so it’s still quite manageable by scanning through. Normally if I’m putting on music from my library I do know specifically what I want to play, if I’m in just a more general mood I’ll put on a Shoutcast station or something along those lines.
To a large degree that same classification can be done by good tags and a solid media player, plus it has the added advantage of being easy for someone else to browse and deal with on all sorts of players. If my wife is trying to play something on from my Tversity server on the PS3 she doesn’t need to know that I’ve classified The Violent Femmes as punk rather than folk, and in that case searching is inconvenient. There is the problem of knowing whether they’d be filed under T or V, but that’s more minor.
And even beyond the bands that don’t neatly fit, do you handle musical style by band, album, or song? If it’s just by band something like On Every Street by Dire Straits will end up massively misclassified. If it’s by album how do you handle Sticky Fingers by The Rolling Stones? And if it’s by song you then need a whole system of playlists to recreate the albums themselves.