Backscatter Machines and Privacy

Over at TalkLeft, there is some discussion of the TSA's planned installation of a body scanner with "backscatter" technology in the Sky Harbor International Airport in Phoenix. The post addresses the technology from a privacy standpoint, but I have a common sense objection to the TSA's stated policy on the use of this machine.

It was interesting to read that the TSA has developed protocols relating to the storage of images from the machine - no images will be stored, and nothing can be printed. Reportedly they have also implemented a "privacy algorithm [which] would eliminate much of the detail shown in the images of the individual while still being effective from a security standpoint" - I guess they digitally put your underwear back on before displaying the image (or perhaps it's more like pasties and a G-string?) I had this discussion with somebody in the federal government quite some time ago, in the context of the use of this technology in federal buildings, and discussed at that time how it should be possible to find a way to process the image to reduce or eliminate the "nudity" without affecting its efficacy. That discussion had nothing to do with the TSA, and has nothing to do with the TSA's recognition of the technological tweaking I had thought obvious. I mention it only because it seems to have taken a long time for the proponents of this technology to implement even modest [no pun intended] changes to the image processing software which would remove a lot of the privacy concerns.

But do we need to be concerned about these machines as an invasion of privacy? Or are they primarily a waste of money.

The security agency's website indicates that the technology will be used initially as a secondary screening measure, meaning that only those passengers who first fail the standard screening process will be directed to the X-ray area.

Even then, passengers will have the option of choosing the backscatter or a traditional pat-down search.

Has any type of cost analysis or efficiency analysis been done to see whether the cost of purchasing and maintaining these machines, and staffing them with technicians, would exceed the cost of, say, adding another agent or two and a few additional curtained areas where pat-downs could be conducted? If a pat-down is a sufficient substitute for the machine, it seems like a huge investment in unnecessary technology. If not, then passengers who wish to smuggle contraband will request a pat-down.

If the plan is to march so many people through the machine that the TSA can't realistically pat them all down, the privacy concern becomes a bit different, as that would make it appear that the criteria for subjecting somebody to this more intensive screening are too lax. One would hope that the plan isn't to loosen screening standards such that a sufficient number of passengers can be marched through the machine so as to justify its cost.