We were packing for a trip to visit my family for Christmas when my daughter asked me why she couldn't bring a bottle of water with her on the plane. I explained to her that, because the bottle carried more than three ounces of liquid, it couldn't be carried on the plane. She asked why, and I told her that it was because someone once tried to blow up an airplane. She didn't quite understand where the three ounce rule came in. I couldn't help her with that one since I don't know either. Three ounces of a liquid explosive could put a nice hole in an airplane. She announced that the rule keeping her from bringing water on the plane was "stupid". I agreed.
It just so happened that soon after this conversation I read this post, in which it was revealed that the Department of Homeland Security was protecting us "24/7, 364 days a year". I showed my daughter this mistake. She rolled her eyes and made a remark about this person being silly. Then I pointed out to her that the person who said this was the person responsible for that "stupid" rule that keeps her from bringing a water bottle on an airplane.