This has been an ongoing event since 1928. I think people who complain about the President joking with these people during wartime, etc., should take a look at the history of the Correspondents' Dinner, which took place through World War II, Korea, and Vietnam. It's part roast, part the president getting to let his hair down, so to speak. Some presidents have been better at this than others, it's always good to see that Bush hasn't lost his sense of humor over the past six years.
I did enjoy the two Presidents! I loved how W could hardly hold his laughter back :-)