Via Bloomberg, Credit Suisse estimates that both Fannie Mae and Freddie Mac face $16 billion in losses for the fourth quarter:

The government-chartered companies’ earnings and capital haven’t yet been hurt by declines in the $230 billion of AAA rated “non-agency” mortgage-backed bonds they hold, according to New York-based analysts Moshe Orenbuch and Kerry Hueston … With other financial companies this quarter already reporting “other than temporary impairments” of mortgage-related holdings that they wouldn’t normally need to report under accounting rules, Fannie Mae and Freddie Mac may need to follow suit, the analysts wrote in a report today. “We believe that this will likely spur the GSEs’ regulator to compel similar actions,” they wrote, referring to the Office of Federal Housing Enterprise Oversight, regulator to the so-called government-sponsored enterprises. McLean, Virginia-based Freddie Mac’s subprime securities may be worth $8 billion to $11 billion less than the prices at which the company is carrying them on its books, while Washington-based Fannie Mae’s bonds may be worth $2.25 billion to $5 billion less, according to Credit Suisse.

These are the sort of losses that could hamper capitalization, without question.