The word is out about how Goldman Sachs and others have been making money. From an Ars Technica article:
If you look under the hood of the markets in 2009, you'll find that the trading floor has been replaced by electronic networks; the frantic, hand-signaling traders have been replaced by computer systems; and all of moves in the trader's dance—a thousand little tricks and techniques (some legal, some questionable, and some outright illegal) for taking regular advantage of speed, location, and information to generate profits—are executed hundreds of times per second, billions of times per day.
Only about three percent of the trading volume on the NYSE is actually carried out by means of traditional "open outcry" trading, where flesh-and-blood humans gather to buy and sell securities. The other 97 percent of NYSE trades are executed via electronic communication networks (ECNs), which, over the past ten years, have rapidly replaced trading floors as the main global venue for buying and selling every asset, derivative, and contract. So the ECNs are the markets in 2009, and those pit traders who pose for the cameras are mainly there for the cameras.
Here's a recent piece from the NY Times:
Powerful computers, some housed right next to the machines that drive marketplaces like the New York Stock Exchange, enable high-frequency traders to transmit millions of orders at lightning speed and, their detractors contend, reap billions at everyone else’s expense.
These systems are so fast they can outsmart or outrun other investors, humans and computers alike. And after growing in the shadows for years, they are generating lots of talk.
Nearly everyone on Wall Street is wondering how hedge funds and large banks like Goldman Sachs are making so much money so soon after the financial system nearly collapsed. High-frequency trading is one answer.
And for some additional enlightenment of the NY Times article:
But then the NY Times gets the bottom line wrong:
The result is that the slower-moving investors paid $1.4 million for about 56,000 shares, or $7,800 more than if they had been able to move as quickly as the high-frequency traders.
No. The disadvantage was not speed. The disadvantage was that the "algos"
had engaged in something other than what their claimed purpose is in the
marketplace - that is, instead of providing liquidity, they intentionally
probed the market with tiny orders that were immediately canceled in a
scheme to gain an illegal view into the other side's willingness to pay.