Security expert (and all around good guy) Bruce Schneier has posted a laundry list of complaints and such regarding the TSA nonsense. One thing that struck me on his analysis was the following quote:
A typical dental X-ray exposes the patient to about 2 millirems of radiation. According to one widely cited estimate, exposing each of 10,000 people to one rem (that is, 1,000 millirems) of radiation will likely lead to 8 excess cancer deaths. Using our assumption of linearity, that means that exposure to the 2 millirems of a typical dental X-ray would lead an individual to have an increased risk of dying from cancer of 16 hundred-thousandths of one percent. Given that very small risk, it is easy to see why most rational people would choose to undergo dental X-rays every few years to protect their teeth.
More importantly for our purposes, assuming that the radiation in a backscatter X-ray is about a hundredth the dose of a dental X-ray, we find that a backscatter X-ray increases the odds of dying from cancer by about 16 ten millionths of one percent. That suggests that for every billion passengers screened with backscatter radiation, about 16 will die from cancer as a result.
Given that there will be 600 million airplane passengers per year, that makes the machines deadlier than the terrorists.