Read his article, and you will understand that this is not a failure of regulation or legislation, but one of world view:

The truth is most of the individual mistakes boil down to just one: a belief that markets are self-adjusting and that the role of government should be minimal. Looking back at that belief during hearings this fall on Capitol Hill, Alan Greenspan said out loud, “I have found a flaw.” Congressman Henry Waxman pushed him, responding, “In other words, you found that your view of the world, your ideology, was not right; it was not working.” “Absolutely, precisely,” Greenspan said. The embrace by America—and much of the rest of the world—of this flawed economic philosophy made it inevitable that we would eventually arrive at the place we are today.

It’s also a very entertaining read.