I realize it's easier to blame one guy -- we all want to point to one person and say: "Him! He's the bad guy!"
Unfortunately, you can't point to the Executive Branch for this. It was Congress who refused to pass regulatory legislation in 2005 that would have provided better oversight of the mort-gage (damn spam filter) industry. The Executive Branch is only responsible for enforcing those regulations.
In fact, in 2005, Congress was warned by one of its members that Fannie-Mae/Freddie-Mac were essentially cooking the books with high-risk loans in order to meet targets that would get their executives bonuses. One member of Congress warned, on the record in open session, that unless there was more regulation the end result would be disastrous for the America's economy.
Unfortunately, those two organizations have some great lobbyists and doled out a lot of money, so the legislation didn't pass ... and here we are.