In her remarks on MSNBC Michelle Obama says of Barak. “His own mother, she said at the beginning of her remarks, was “very young and very single when she had him.” ”

Its reasonable to conclude that the Obama campaign would be hesitant to release his birth certificate because it would show that he was born illegitimate. Since a significant porportion of the US population is illegitimate–you would think that this would not be a problem for the obama campaign. So it might be something else. But maybe not.