In 2000 I took off and landed 28 times. I received extra scrutiny on three occasions. Once in Norfolk,Va when I had an anniversary clock in my carry-on(received the swatch/explosive screen) Once in Pittsburgh when I stepped outside for a cigarette (again the swatch test) and a third time at Chicago Midway when my carryone was full of chips and a few strikes. They do look at you funny when you have a bag full of little clay discs.