Two cool bits of trivia from this article:
1) "The thicker the dip, the more stuck to the chip, and so the fewer bacteria were left behind in the bowl."
2) The 1993 Sienfeld episode is the "first notable use of 'double dip' to mean dipping a chip twice".
Check out the NY Times article here to see how much bacteria is in your dip before you start munching at the Super Bowl this weekend. (Thanks Danny!)