The following sums it up:
“Fannie Mae has not changed its criteria for evaluating loans for potential repurchase,” Andrew Wilson, a spokesman for the Washington-based firm, said in an e-mailed statement. “What changed was the volume of loans from 2005-2008 that did not meet our standards and therefore must be repurchased by lenders.”
It's clear that Freddie and Fannie weren't the prime reason for the crash that some have made them out to be. However, it's obvious that Freddie and Fannie weren't doing proper due-diligence before the crash. The lack of regulatory oversight (bank auditors with governmental power) of the entire bubble was gigantic.