The $600 billion is not real money. Imagine a casino that approves bets worth more than the house. Lets say the house is woth $1000. I pay them $5 for a high odds bet that returns $1,000,000. I win. The casino goes broke and all sorts of other bad things happen, but did the $1,000,000 ever exist? Not on your life. Yet $600 billion is being reported as if it was real money that will have a real effect on the global economy.

And as for Greenspan - this "market" thing he talks about is not a market I would recognise. In the markets I know and love, everybody knows what is being bought and sold. No one can claim to be selling a 1Kg of gold, but then deliver 1Kg of lead painted with gold. Allowing this would kill the market, obviously.

Greenspan and his "free-market" mates created the conditions under which that could happen. Under the guise of "removing regulation" to allow the "markets to be free", he removed the oversight. That oversight created the transparency which meant everyone knew what was going on. Example: look up CDO's on wikipedia. They are really an insurance policy on a loan but called a CDO to avoid the tight regulations on insurance. As a consequence people insured things with CDO's they didn't own. Effectively CDO's became bets on whether loan would be repaid, or ultimately on whether a company would fail. I hope the connection to the casino example is obvious.

In general, if everyone is going to understand what is bought and sold things have to be kept simple. Thus regulation has a lot to say about what can be bought and sold, to keep arbitrarily complex things from getting to the market. In the financial world, complexity is the paint on the lead. It is no accident that the destruction of our financial markets was proceeded by a sharp rise in complex derivatives.

There is nothing wrong with derivatives, provided everybody knows what they are. Greenspan oversaw the removal of the rules ensuring everybody did know.