Only days after Freddie Mac sought a $6-billion cash lifeline from the Treasury Department, Fannie Mae is now chasing a $7.8-billion check in federal aid. Attributing its steep $5.1-billion third-quarter deficit to losses on derivatives and the persistent failings of the housing market, the government-controlled firm is furthering its heedless course to fiscal Armageddon — while draining the bank accounts of American taxpayers all along the way. Fannie Mae and its cohort Freddie Mac were seized by the federal government during the financial crisis as company executives pleaded that severe losses on subprime mortgages were foreboding their insolvency. Considering their vast presence in housing finance, owning or guaranteeing roughly half of all outstanding mortgages (including other federal agencies, they have backed about 90 percent of new mortgages over the past year), the government has pledged an endless stream of funds to the two government-sponsored enterprises through the end of 2012, which has left taxpayers on the hook for a combined total of $169 billion. The general functions of Fannie and Freddie are to purchase home loans from banks and lenders, package the loans with bonds — while guaranteeing them against default — and sell them to investors inside and outside of the United States. But between 2005 and 2008, Fannie and Freddie carelessly purchased a heap of bad mortgages, which nearly buried the two companies into foreclosure themselves.