As government probes into Barclay's abuse of private "dark pool" trading widen to include similar allegations of fraud perpetrated by UBS and Deutsche Bank, the public and lawmakers are demanding to know one thing: What novelty hot sauces induced brokers to let their clients trade in these dangerous venues?

Fitted to excite pity and sympathy, state and federal agencies have begun filing lawsuits against financial services juggernaut and arguable maîtres du monde Barclays PLC over allegations of fraud at Liquidity Cross: the British firm's "dark pool" trading venue. Yes. Fraud. In a dark pool.