Originally Posted by
n5667
Just pull out a tape recorder and start recording when you put it in a bin...

According to the signs at BWI, you'd be breaking the law (Maryland) to do that at a checkpoint (there's another thread about that somewhere). I think I have a stronger case if I'm polite and I'm not breaking the posted regulations (whether they're enforceable or not is a different question).
As a result, the screeners at BWI operate with total impunity.