According to Investor's Business Daily this problem all started during the Clinton administration.

"The Clinton administration, obsessed with multiculturalism, dictated where mortgage lenders could lend, and originally helped create the market for high-risk areas where they had no choice but to lower standards to make the loans that sound business pratices had previously guarded against making. It was either that or face stiff government penalties. It was the Clinton administration that mismanged the quasi-governmental agencies tht over the decades have come to manage the real estate in America. When Clinton crony Franklin Delano Raines took over the helm of Fannie Mae, in 1999 he used it as his own personal piggy bank, looting it for a total of 100 million in compenssation by the time he left in early 2005 under an ethical cloud."

This is only a portion of the article. More examples are given to clarify their point. I don't know how much, if any, of this is true. Just thought I'd give a different view point.