U2 vocalist, Bono, is about to become the world's wealthiest musician.  Bono's equity firm, Elevation Partners, gave $90 million to Facebook in 2009, which earned them a 2.3% stake in the company.  With Facebook on the verge of going public, that $90 million investment is expected to be worth more than $1.5 billion.  Bono will surpass Paul McCartney whose has an estimated worth of just over a billion dollars.