Inquiring minds have been wondering just how hedge funds and banks like Goldman Sachs are raking in the dough in the wake of the financial meltdown. The answer may be a new hustle called high-frequency trading.

How it works: Powerful computers allow high-frequency traders to trade at warp speed, outrunning other investors. Issuing and canceling orders nearly simultaneously, this small group of traders gets an early look at how others are trading through a loophole in market rules. Good-bye, transparency. Hello, unfair advantage. Goldman Sachs, naturally, is in on the game, but also, naturally, denies that it is getting an unfair advantage. But the money sure is piling up...

As daily volume on the stock market skyrockets, critics are asking if this new ‘technological arms race' will produce a two-tiered marketplace of those who can place the high-frequency arbitrage game, and all the other poor suckers. s on steroids. And that's pretty scary.