George Soros gained global recognition when he co-founded the Quantum Fund with Jim Rogers in 1970. That fund generated an average annual return of more than 30% while he was at the helm. Soros hasn't quit making timely market calls since: From his $10 billion bet against the British pound sterling in 1992 to his April 2008 prediction that we had not "seen the full effect" of the recession and that the situation was "more serious than the authorities admit or recognize." In February, Soros called the euro's viability into question , and the currency has plunged some 10% since that time.