If you believe the U.S. House of Representatives

That is, the U.S. House of Representatives Committee on Oversight and Government Reform:

The housing bubble that burst in 2007 and led to a financial crisis can be traced back to federal government intervention in the U.S. housing market intended to help provide homeownership opportunities for more Americans. This intervention began with two government-backed corporations, Fannie Mae and Freddie Mac, which privatized their profits but socialized their risks, creating powerful incentives for them to act recklessly and exposing taxpayers to tremendous losses. Government intervention also created “affordable” but dangerous lending policies which encouraged lower down payments, looser underwriting standards and higher leverage.

Finally, government intervention created a nexus of vested interests – politicians, lenders and lobbyists – who profited from the “affordable” housing market and acted to kill reforms. In the short run, this government intervention was successful in its stated goal – raising the national homeownership rate. However, the ultimate effect was to create a mortgage tsunami that wrought devastation on the American people and economy. While government intervention was not the sole cause of the financial crisis, its role was significant and has received too little attention.

via CARPE DIEM