Not only would the tax reduce risk and volatility in the market, but it would also raise much-needed revenue for public coffers while making it modestly more expensive to engage in a practice that brings little overall economic benefit. High-frequency trading is essentially “computerized scalping” that allows trading firms with the fastest algorithms and speediest machines to front-run other investors. The spreads are tiny, but multiplied billions of times those fractions of a cent add up rapidly, whether as a windfall for traders or slightly higher prices for ordinary investors. High frequency trading firms are notoriously silent when it comes to the in's and out's of how they do their business. MIT Tech Review had a long article discussing their role in the 2008 crash as well. Algorithms shouldn't be allowed to have such a prominent role in our daily stock trading. They also cater to the Uber wealthy.