One of the biggest Bitcoin exchanges has filed for Chapter 15 bankruptcy protection in the United States, which is for insolvent companies operating internationally. On Feb. 28, Mt. Gox filed for bankruptcy protection in Japan after losing what amounted to about $500 million in Bitcoins due to “weaknesses in the system,” said CEO Mark Karpeles. By filing in the U.S., Mt. Gox has put at least a temporary hold against a lawsuit filed in a Chicago federal court seeking class-action status.