Honestly I can't imagine someone who hasn't been living under a rock for the last half century could say this. Just one example: Knight Capitol was the largest trader in U.S. equities, with a market share of 17.3% on NYSE and 16.9% on NASDAQ in 2012, right up until August 1, 2012, when it lost $460 million and 75% of its equity value because of a software error. What was left of it was acquired in December of that year.