A trader rubs his eyes on the floor of the New York Stock Exchange before the closing bell Friday. The Dow Jones industrial average closed down nearly 140 points for the day and 600 points for the week (Mario Tama / Getty Images / May 7, 2010)

So much for the biggest, safest, most liquid securities market in the world.

Of course we're talking about the U.S. equities market, which used to be described in those glowing terms. But now, after Thursday's trading debacle, the market looks more like a casino — and not just any casino, but one of those smelly joints with sawdust on the floor, ripped felt on the blackjack tables and loaded dice.

I've been inside casinos like that. I wouldn't think of laying a 10-cent bet with the dealer. So why would I buy stock on an exchange emitting the same odor of rancid beer?

The market's friends, including executives of the various exchanges and some traders with access to turbocharged equipment, would like us to think that the system worked Thursday. This is based on the idea that things could have been a lot worse.