Music's superstars are no longer just relying on shrinking recorded music sales or touring revenue to make their millions. Bono's investment firm scored big on the Facebook IPO. Mariah Carey just became the highest paid reality tv star ever. Justin Beiber is spreading his investments over many smaller music and social tech startups; while Justin Timberlake is focusing on rejuvenating MySpace. As music's revenue streams shift radically, who are the world's richest musicians?