Housingwire reports that Fannie Mae and Freddie Mac are two of the worst performing stocks of 2010. The government-sponsored enterprises ranked as the fifth-worst and third-worst stocks of the Fortune 500 with price declines of 79 percent and 74 percent. The companies were put into federal conservatorship in September, 2008 after amassing losses upward of $12 billion. According to CNNMoney, some estimate Fannie Mae and Freddie Mac may ultimately cost the government up to $1 trillion.