Today, I had my toothpaste confiscated at the airport. I asked the TSA screener if my toothpaste was actually a threat to national security. She said, with perfect sincerity, "Yes, it is. But you can go and check it, if you want to pick it up in Las Vegas."
From this I divine that toothpaste itself is not actually a threat - but rather, my access to that toothpaste. Toothpaste on the plane is not a problem. But me in the presence of toothpaste, can somehow result in a terrorist attack. "Open the cabin door, American infidels, or I will make you SO MINTY!"
Oh, but also, I can have up to 3.4 oz of toothpaste. I argued that since my 4oz tube was half empty, it was actually quite a bit less than 3.4 oz. (Apparently the dangerously minty threshhold is somewhere around 4 oz.) This logic was defeated by bureacratic ass-headedness.
This policy makes no sense. Look forward to a strongly worded letter to the director of the TSA in the near future.