Still, those profits weren't enough. Their customers were making great money buying Wall Street's derivatives. But why should banks and pension funds and hedge funds have all the fun? What a perfect use for all that capital on their huge balance sheets and cheap financing from low interest rates. Wall Street, en masse, started buying all these high yielding derivatives for their own account. They ate their own dog food, if you will.

It was the easy trade. Borrow at 3 percent and make 6 percent or 8 percent or 10 percent. They liked it so much, they levered up. Meaning instead of just borrowing a dollar for every two dollars of assets they owned (which by the way, thanks to the 50-percent margin requirement, is the amount of leverage that you and I are allowed to buy stocks from these same firms), they borrowed 20 to 1, 30 to 1, and even 50 to 1, if they could get away with it. And man, it was a lucrative trade. So why not?

I'll tell you why not. Because all of a sudden, Wall Street is no longer a business of traders or stock brokers or investment bankers, it's a giant hedge fund. And they have no idea what they are doing. None. I ran a hedge fund for a lot of years and learned rather quickly that if a trade was too good, if everyone was doing the same trade, then I should absolutely turn around and run for the hills. But no one on Wall Street did. The spreadsheets flashed green. Risk was a four-letter word best not said in polite company. Wall Streeters became hedge fund cowboys and loved the spoils, until a tiny little downturn in housing sent everyone rushing to get out of the pool at the same time.