Digital currency Bitcoin has grown sensationally, with 11 million Bitcoins worth nearly $2 billion in circulation. It's the ultimate Internet-age currency: Bitcoin circulates only online, trades anonymously and isn't regulated by any government.
Whenever there's a big economic crisis, investors usually flock to the safety of gold or U.S. government bonds. But when things got crazy in the last couple weeks in Cyprus, it was something called Bitcoin that surged in value.
