The hazard of leaving it on the balance sheet is the Fed having massive exposure to something that they probably shouldn't. Which isn't really a problem... bec

The hazard of leaving it on the balance sheet is the Fed having massive exposure to something that they probably shouldn't. Which isn't really a problem... because it's impossible for the Fed to get called in the way a bank would if there's a housing crash. But is probably less than ideal... as it's just weird to have the Fed holding that much mortgage debt directly.