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The new structure of the U.S. stock market had removed the big Wall Street banks from their historic, lucrative role as intermediary. At the same time it created, for any big bank, some unpleasant risks: that the customer would somehow figure out what was happening to his stock market orders. And that the technology might somehow go wrong. If the markets collapsed, or if another flash crash occurred, the high-frequency traders would not take 85 percent of the blame, or bear 85 percent of the costs of the inevitable lawsuits. The banks would bear the lion’s share of the blame and the costs. The relationship of the big Wall Street banks to the high-frequency traders, when you thought about it, was a bit like the relationship of the entire society to the big Wall Street banks. When things went well, the HFT guys took most of the gains; when things went badly, the HFT guys vanished and the banks took the losses.
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