An Adaptation From ‘Flash Boys: A Wall Street Revolt,’

The trouble with the stock market — with all of the public and private exchanges — was that they were fantastically gameable, and had been gamed: first by clever guys in small shops, and then by prop traders who moved inside the big Wall Street banks. That was the problem, Puz thought. From the point of view of the most sophisticated traders, the stock market wasn’t a mechanism for channeling capital to productive enterprise but a puzzle to be solved. “Investing shouldn’t be about gaming a system,” he says. “It should be about something else.”

via An Adaptation From ‘Flash Boys: A Wall Street Revolt,’ by Michael Lewis –

The same system that once gave us subprime-mortgage collateralized debt obligations no investor could possibly truly understand now gave us stock-market trades involving fractions of a penny that occurred at unsafe speeds using order types that no investor could possibly truly understand. That is why Brad Katsuyama’s desire to explain things so that others would understand was so seditious. He attacked the newly automated financial system at its core, where the money was made from its incomprehensibility.

Update:  For some highly technical information on High Frequency Trading I was pointed to this set of articles from ACM, Association of Computing Machinery.