While I'm not defending the porn scanners or pat downs, I think the reason for requiring flight crews to go through security is because it isn't to difficult to obtain a uniform and badge if you want to take down a plane. Buy a ticket the day before, stick it in the pocket of your uniform and go through with your fake badge. Change clothes in the bathroom and board the plane with your weapon. Having a fingerprint or iris scanner with previously cleared employees info on the network wouldn't be too hard to implement. I think they were going to do that with frequent fliers, but I haven't seen one yet.