[jamesseda]

If G-mail didn't exist I would use yahoo. G-mail is much better for me though. I win and Google wins. Yahoo looses. If GS gets in front of Citi on a trade by 2 seconds GS wins and Citi looses, no one else is involved. Unless those two seconds of "efficiency" help someone?

[yummyfajitas]

You are assuming all trades are determined by priority, which is false.

If GS got there first, but Citi cuts in line by offering a better price, the customer also wins.