Paul McCartney may be about to be surpassed as the wealthiest rock musician in the world by Bono. The U2 frontman who owns a 2.3 percent stake in Facebook, is expected to see his net worth increase significantly when the social-networking company goes public.

Facebook is valued at more than $100 billion, which will make Bono's share worth in excess of $1.5 billion.  In comparison, Paul's  fortune is estimated to be slightly over $1 billion.

Bono bought his Facebook shares for about $90 million back in 2009.