What would you do with $700 Billion?
semblance2: Since it seems like defaulting mortgages are the cause of the situation, why not use the money to pay off those mortgages?.  If it took $50,000 on average to save an individual mortgage, then you could rescue 14 million mortgages.  Some would say that presents a moral hazard, but it seems like that cat is way out of the bag already.