"But what about the Obama-Ahmadinejad handshake? There's no question of a true incident being misremembered: The two men have never been physically close enough to be photographed together. (We searched for them in Google Images and gave up after scanning 500 results.)"
That presence or absence on Google Images is sufficient to constitute proof. Which isn't to say Obama's secretly shaking hands in underground bunkers. I am, however, interacting more and more with people who seem to think that if they can't find it on Google, it doesn't exist.