Fannie Mae and Freddie Mac reported somewhat underwhelming results for the fourth quarter, thanks to huge hits they took from hedging losses tied to their holdings of derivatives. The reduced earnings highlighted the fact that although the two have been cash cows for the U.S. Treasury over the past two years, they aren’t bullet proof. During separate press briefings with the media, the CEOs of both firms spent a bit of time going over the hits they took on their derivatives, stressing that the interest rate swaps they use to hedge rate swings are essential and cut both ways. The message was clear: if mortgage rates had not fallen dramatically in December, their earnings would have been ... [with one exclusive chart] ...