OK, for every other example, we're going to stay out of the pop realm and stick with rock star-on-rock star action. However, when you manage to piss off one of the peace-loving Beatles like Michael Jackson did in 1985, you earn yourself a spot on this list.

As the story goes, Paul McCartney made a big mistake sharing his investing advice with Jackson. After he told his two-time duet partner how much money could be made by buying the publishing rights to hit songs, the "King of Pop" turned around and bought the company that owned most of the Fab Four's catalog. "I think it's dodgy to do things like that," was McCartney's surprisingly measured response, "to be someone's friend and then buy the rug they're standing on."