60 Minutes: The bets that brought down Wall St. | Crooks and Liars

"In essence, speculators bet that homeowners wouldn't be unable to pay back their mortgages, and when those people started defaulting and the speculators tried to cash in their wagers, there was no money to cover the literally trillions of dollars in payouts. What it really boils down to is an unregulated gambling racket that Congress voted unanimously to create and legalize."