The price of Bitcoin has plummeted 11.2% to $484.35 after one of its leading exchanges, Mt Gox, appeared to have disappeared amid speculation of a massive security breach and that it's about to go bankrupt.
Mt Gox's Web site was blank this morning and all its tweets have been deleted. Since the start of this month, customers had been unable to withdraw their bitcoins. On Sunday, CEO Mark Karpeles resigned from the board of the Bitcoin Foundation.
One rumor, based on a leaked document, is that 744,400 bitcoins worth $350M have been stolen from Mt Gox, or 6% of all bitcoins in existence.
Six other major bitcoin exchanges and businesses have said they'll work together to reassure customers about the security of their funds.
Meanwhile, security firm Trustwave yesterday said hundreds of thousands of computers have been infected with a virus called "Pony" that allows thieves to steal digital currencies such as bitcoins.