My desk lamp also uses an electrical plug to connect to power. It isn't inconceivable that it could receive more power than intended and blind me! By the way, an order of magnitude or two more radiation than intended would be equivalent to a dental xray.

Look, I'm not saying your fear is physically impossible. I'm just saying I can't think of a very many machines (radiation sources or otherwise) for which anything similar is a plausible fear. Most machines simply stop working when used outside their operating parameters.

Also, do you really think that if the backscattering machine emitted the wrong type of radiation (x-rays of a different frequency), the TSA agent operating the scanner wouldn't notice when his screen went blank (unless the detectors simultaneously malfunctioned to pick up the incorrect frequency)?