U.S. regulator says 'flash crash' manipulation hard to detect

By Suzanne Barlyn CHICAGO (Reuters) - The type of alleged market manipulation by the British trader accused of helping provoke the "flash crash" in 2010 is hard to detect, the chief of the Financial Industry Regulatory Authority said on Friday. Nonetheless, the alleged abuses were "somewhat surprising" given that his behaviour was identified in 2009 but continued for another five years, said Richard Ketchum, chairman and chief executive of FINRA, a self-funded regulator for Wall Street. "I won't