It’s not greed, silly. People are greedy when the economy expands, too. The problem was that the government distorted the market, and no one knew when they should stop lest their greed be thwarted.
The government didn't come up with negative amortization loans, no documentation loans, interest only loans. The government didn't force mortgage brokers to give mortgages to people 30 time greater than their income. The mortgage brokers came up with that on their own.
Greed is good.
Greed at the taxpayer’s expense is not good.
Fannie/Freddie and the Investment Banks that were their partners (e.g, Corzine) are the problem.
Also, borrowers need to receive a large chunk of the blame. Without them, there was no demand for CRA and Fannie/Freddie products.