“Most of the time, it works great. Most of the time, computerized trading makes stock markets more efficient, and it’s easier and cheaper for investors, both large and small, to trade. And it’s a good thing for everybody. But every so often, things can go horribly wrong, and we don’t know when and we don’t know how and we don’t know what the consequences might be. And that huge uncertainty, I think, is the biggest danger in the markets right now.” —Financial reporter Felix Salmon explains the itty-bitty downside to automated high-frequency trading, the same technology behind the “flash crash” that helped a single $4.1 billion trade cause the Dow to drop hundreds of points in a matter of minutes. But other than the pervasive sense of potential doom lurking behind every once-or-twice-per-millisecond trade, it’s pretty neat stuff.