See I don't feel safer when I am screened because I know that I am not trying to do harm to anyone and the TSA is simply wasting my time and money by screening everyone in this manner. "But how do WE know that you are not trying to do harm?" the screeners will say. And the response back is that if you are trying to secure something, the least efficient way to do that is to try and check EVERYTHING. What you should really do is rule out those things that will not cause damage and then concentrate your efforts on those things that are more likely to do damage. Rounded scissors from a 4 year old couldn't hurt anything. An aluminum soda can on the other hand could be deadly. One is confiscated as being a "threat" the other is handed out free on almost every flight.
If we really wanted to secure these planes we would concentrate the efforts on finding out who the bad guys are and not let them on the planes. The circus we see every day at the airports is simply a show for the public to make them feel safe. We are no safer today then we were before 9/11. See the discussion on spotting the FAM if you want to see even more stupidity in action.