IMO, the full-body scanners, the puffers and the rest are a consequence of the gov't R&D funding game. Here's how you play: Nerdy researcher in some university lab comes up with a neat piece of technology and thinks "What could this be used for and who will pay for that?" So they define a problem to which this piece of gear is the answer, and find someone with deep pockets who could be convinced the problem exists. Given the paranoia at TSA, it's not hard to convince them that there's a threat that could be eliminated by using My Expensive New Device. TSA writes a big honking cheque before the paint is dry on the first prototype. When it fails in the real world (puffers, anyone?), it's not the researcher's fault. He's on his next project, using your tax dollars.

Seriously, (in the hands of a really skilled operator) a good x-ray machine and WTMD would identify, what, about 99.9% of actual threats? (I don't consider shampoo a threat.) Maybe adding the full-body scanner makes that 99.95%. With the puffer as well, maybe 99.97%. No matter what, you're never going to get 100%, but TSA will keep spending your tax dollars (and wasting your time, and invading your privacy) trying. And when TSA's score with x-ray/WTMD is more like 30 to 50%, it's idiotic to keep adding more machines to try to diminish the risks.

I'm not against research per se - it's my life - but there's far too much "solution looking for a problem" going on.