Last December, Fannie Mae’s stock was sitting at about $74 per share – even as its top two executives were on the hot seat after the eruption of an accounting scandal. During the past nine months, the government-sponsored enterprise has overhauled its management team and rebuilt its capital base. But Fannie’s stock has sunk 40 percent – approximately $28 billion in market value – and recent numbers indicate investors don’t consider Fannie worth its…