Mark W. Shead has a blog with, well, just some interesting stuff.  He writes about some productivity things but a lot of the rest...well...read this from one of his posts.

In 1995 two bank robberies were performed by an individual wearing no disguise. The surveillance tapes insured that he was arrested the same day. When he was shown the videos he was amazed that they could see his face. He said, “but I wore the juice”. Evidentially he had been told that putting lemon juice on your face would keep it from showing up on security cameras.

Now, I'm not sure what the average intelligence or gullibility of bank robbers may be.  But I'm sure interested in hearing who convinced these bank robbers that lemon juice makes you invisible to security cameras.  Think of all the other things that people can be persuaded to believe...  It truly boggles the mind.

Because I wasn't too sure about the validity of this story, I looked around and found some other references to it.

Over at Mindhacks.com they use the story as an example that "when we’re incompetent at something we’re often so incompetent that we don’t realize that we’re incompetent." I even found it referenced on a New York Times Blog.