The uproar over David Letterman's unfunny joke about Sarah Palin's daughter demonstrated that even a deft comedian gets his timing wrong. According to the nonpartisan Center for Media and Public Affairs, the late-night tally of jokes about Bristol Palin's pregnancy included, as of mid-March: Conan O'Brien, 20; Jay Leno, 15; Letterman, eight; Jon Stewart, four. Some were twofers, joking about the sexual activity of John Edwards and pro hockey players. "Saturday Night Live" even did a joke about incest — just a few weeks before Sarah Palin was a guest on the show. Letterman didn't help himself by getting his teenage Palins confused in the latest joke. But "why did this one draw such a reaction?" asked Philadelphia Inquirer columnist Michael Smerconish. "Letterman's timing was waaaay off."