There were a majority of people who actually had great credit. And they speculated that the real estate bubble would continue to boom. What happened when a lot of people defaulted on their loans? Their speculation busted. All of a sudden, their property values go down. Greed on people who want a home even though they willingly know they couldn't afford one, and greed on other people who want to flip-flop a house. This show
http://www.aetv.com/flipthishouse/, I am sure made people even more greedier.
That couple who were doing nice and whom I assume had bought a home they could afford, surely didn't see this happening. They were just being good, hard working, paying their taxes folks.