The implosion of MF Global Holdings Ltd, the largest independent U.S. futures broker until it filed for bankruptcy protection on Monday, calls to mind the collapse of Refco – which in its time was the largest independent U.S. futures broker – after revelations that Refco’s CEO had defrauded his investors. (London hedge fund company Man Group Plc bought Refco’s futures brokerage just about six years ago, and later spun off its brokerage and renamed it MF Global.)