There may have been more articles written about people not telling jokes about Obama than there have been actual jokes about Obama.
What's inexplicable about this continual and terrible line of stories is that not a single one of the comedians complaining that nobody tells jokes about Obama seems to be making an effort to make jokes about Obama - and if they are, they usually fail not because of some fear they have of being declared racist, but instead because they're fucking bad at jokes.
Of course, there is something to this I-don't-wanna-be-racist idea. Political comedians aren't telling a lot of jokes about Obama is that the first people to fill in the gap of anti-Obama humor were generally crazy-ass racists sending you e-mails about how Obama is going to walk out for the State of the Union with a pick in his hair or how he's going to be missing briefings because he's got to find a place to put down his prayer mat. Mainstream political humor is nothing if not trail-following rather than trailblazing; Jay Leno will be telling Lewinsky jokes until she's elected Secretary General of the United Nations. When the main model for Obama mockery sits one or two steps removed from (or in the case of Glenn Beck, one step past) the worries that he's going to turn the Rose Garden into a cotton field, it's hard to get any popular momentum for the allegedly funny things about the guy.
Nobody wants to laugh at something that makes them feel uncomfortably close to being their own racist uncle. That gets into all sorts of weird incest/time-travel shit, and this is not Backwoods Quantum Leap.