While it's great U2 raked in $130 million last year as the world's biggest-selling music act, according to Forbes, that sum wouldn't even cover the amount Bono lost on his worst investment. When Bono bought a stake in private equity firm Elevation Partners in 2004, it gave him a nearly 30% stake in Palm, including stock worth an estimated $325 million. In the pre-iPhone smartphone market, that wasn't too shabby. When Palm fumbled the Pre, however, and the iPhone surged in market share, that investment started to look a lot more shaky. It got worse when H-P ( HPQ) bought Palm for $1.2 billion last year, but only valued Palm shares at $5.70 when they were trading at $18 just a year before. The whole deal set Bono back $140 million and, while it's tough to top U2's Pop album as a career low point, his disastrous Palm investment trumped it in Bono's typically grand fashion.