Bruce Schneier interview with Kip Hawley, Part I:

Kip Hawley: Screening ideas are indeed thought up by the Office for Annoying Air Travelers and vetted through the Directorate for Confusion and Complexity, and then we review them to insure that there are sufficient unintended irritating consequences so that the blogosphere is constantly fueled.

Aha! We've had our hunches.

Imagine for a moment that TSA people are somewhat bright, and motivated to protect the public with the least intrusion into their lives, not to mention travel themselves. How might you engineer backwards from that premise to get to three ounces and a baggie?

The Vice President has investments in a company that manufacturers sample-size bottles.