Over the past few weeks, speculators have been driving up the price of Fannie Mae and Freddie Mac common stock and “trust” preferred shares in the hope of a payoff somewhere down the line. But according to interviews conducted by Inside Mortgage Finance, the only payoff might come if they can find someone else willing to pay more than they did for stock that is considered virtually worthless. Industry lobbyists, former government-sponsored enterprise executives and some investors say...