A friend of mine was traveling through various airports in the states. He had accidentally left his pencil bag in his back pack which had a pair of scissors in it. The scissors were over the length allowed on a plaine (Something like 4" is considered safe.)
He went through 2 security checks in the states, and boarded planes with these scissors in his back pack. It wasn't until he went through a simple, small security check in a small Canadian air port that they were found and confiscated.
I find it funny that he made it through all this elaborate security in the States, and a simple security check in Canada with a Security guard who did his job well found the scissors.