Far be it from me to come up with unique content. So, here's more of someone else's stuff.
Now, let's assume that this wasn't a complete put-on, and that some of these receipts are legitimate. Can any of the scientists in the audience tell me how the author fails to preserve the integrity of his "experiment?" If you said, "by conspicuously snapping pictures of his wacky signature, thus suggesting to each clerk and waiter that he's probably not trying to surreptitiously rip somebody off," you win.
Sure, his point is that a "good" employee would be a dick and force him to re-do the signature for real. But who would make such a spectacle of himself while trying to sneak something past the credit card's real owner? He basically identified himself by taking these goofy pictures. The real question should be "how much do I need to spend before someone decides that my wacky behavior is insufficient identification?"
All in all, though, good prank. It's not the Upper Decker or anything, but pretty good.