Maybe I suck at basic prob/stats but if you remove the scanners, I bet the chance of a plane getting blown up by a terrorist is significantly increased. ;)
1- Pilots with guns & keeping the doors closed for the full flight
2- Passengers not willing to allow others on the plane do harm to the plane. If passengers see things happen now, they will stand up and makes attempts to stop them. We won't have a 9/11 style hijacking. Even if someone gets a box cutter in, people will take them down before they'll let them take the plane.
I can't imagine how these body scanners would make us significantly safer.
It seems that once something is identified a threat, it will always now be seen as a threat.
http://www.youtube.com/watch?v=3V9MD15qs5s http://www.abovetopsecret.com/forum/thread624915/pg1
But the real point is that now no one would allow a few guys with boxcutters to take over the plane in the first place. They aren't getting in the cockpit, because that isn't going to open in almost any circumstance.
I know if I see some guy stand up and start threatening the plane, I will do whatever it takes to disarm and disable them with what I have available on me- even if I am outmatched physically by size or weaponry. I'd feel certain that if other passengers think that someone is going to take over the plane, they will help out.