One of Bitcoin enthusiast Mike Caldwell's coins in this photo illustration at his office in Sandy, Utah, September 17, 2013. Bitcoins, touted by some experts as the future of money, gained in prominence during Europe's financial crisis as more people questioned the safety of holding their cash in the bank. Cameron and Tyler Winklevoss, currently making headlines with plans to launch a Bitcoin fund, said on Tuesday that they could see the digital currency becoming a country's official money. REUTERS/Jim Urquhart (UNITED STATES - Tags: BUSINESS SOCIETY)