Gregg, you thread stealer you!!!
Anyway, my list:
The Rolling Stones - Obviously this should have happened in 1970 or so. Contributes nothing to the music world except for overpriced tours.
Red Hot Chili Peppers, Pearl Jam, The Beastie Boys, etc. - Bands that crank out an album every few years, where upon everyone goes "Hey, remember when they were awesome in 199X?"
Snoop Dogg and Ice Cube- If you're doing family movies, your hardcore street cred is somewhere around ZERO.
Foo Fighters- Every album somehow gets progressively more slick, overproduced, and more boring. I don't mind Dave showboating (which is basically all FF is), but the music has to mean something. You were in Nirvana, dude.
And basically alot of other bands. I think the general idea is if you're rehashing your old hits and not making any musical progress, call it a day. Fans will be a lot happier with a smaller discography of kick ass albums versus a lot of albums, but most of them suck.