Sure, but someone that wants to get a glass knife through airport security can come up with much better ways of doing it.

My dad and I occasionally play a game where we try to one-up each-other with ways to get weapons or contraband through security. There are a lot of ways. These backscatter scanners -- like most of the rest of airport security -- do very little to actually increase the security of the system.

Also: http://xkcd.com/651/