There are multiple problems with TSA screening in general, and backscatter machines in particular, which are listed below.

As these machines are ill-advised, you currently have the option to "opt out" and receive a pat-down instead.

PAT-DOWNS:

New guidelines just instituted for the pat-down procedure include groping of breasts, buttocks, and crotches. [8][15]
Even for minors. [13] [14]

"My wife tells me that they grabbed my [10-year-old] son's privates and he was crying the whole time and all she could do was stand there and tell him it was going to be OK." [16]

Due to this, the ACLU is now taking reports of pat-down abuse:

http://www.aclu.org/technology-and-liberty/tsa-pat-down-sear...

Note that going through a scan does NOT exempt you from a pat-down grope. You may be groped if you trigger a metal detector, or if your backscatter shows an "anomaly", or for any other reason or no reason at all. There are also gate screenings, where you will be pulled aside at the gate, and since there are no machines, you will be patted down / groped.

IMPACT

About 1 in 5 people are sexually assaulted by age 18. [1]

This means that even "normal" pat-downs are extremely distressing or damaging to a significant percentage of the population, and these new procedures are simply sexual assault under color of authority, which can be traumatic. Victims of sexual assault, molestation, and rape often feel like they are re-living their experiences, and even those who don't have such a background may experience emotional damage from the procedure.

I defy anyone to belittle the experience of victims of sexual abuse, who do not want any unwanted touching forced upon them, least of all groping of private areas.

BACKSCATTER SCANS

All the official images have been redacted. Here is what it REALLY looks like, scaled down:

http://dams.rca.ac.uk/res/sites/Show2006/Images06/John_Wild_...

This is an artist's self-portrait. In addition to clearly seeing his genitals, note the penetration into his kneecaps, shin bones, and feet. Then consider the unprotected areas, such as face, neck, and eyes. Look more closely and you can see the bones in his forearms (radius, ulna), part of his humerus, and his hands.

Then consider the findings of people like David Brenner, the head of Columbia University’s Center for Radiological Research, who explains that the dose is actually 20 times higher than the official estimate. [2] [3] [4] [5]

The energy is absorbed mostly in the skin, NOT throughout the volume of the entire body as with other types of ionizing radiation. Also, the dosage is delivered in a few (under 30) seconds. You have to consider dose per unit time; the figures often mentioned for long flights mention the total dose, which is distributed over a period of HOURS.

PRIVACY

The TSA originally claimed that these machines were simply INCAPABLE of storing images. That wasn't true:

"The documents, released by the Department of Homeland Security, reveal that Whole Body Imaging machines can record, store, and transmit digital strip search images of Americans" [6]

This also goes for MMW (millimeter wave) machines used by courthouses:

"Feds admit storing checkpoint body scan images" [7]

ANONYMITY

Some locations are now using a full-color video camera in addition to the backscatter / MMW imager. This means your full-body color portrait and unclothed image can be linked; and if they scan your boarding pass or other identifying information, they can link your images to your name and other personal information (phone number, address, BIRTH DATE). [12]

SLIPPERY SLOPE

Originally the TSA claimed the backscatter machines were optional and there was no penalty for declining (no groping); that they had no capability to store images; that they would NEVER be used as primary screening instead of metal detectors (now they ARE being used as primary screening in some airports with plans for the rest -- see [9] [10]).

The supposed motivation for storing images would be in case of another attempt like the underwear bomber, to go back and "check the tapes" to see what they missed.

You should probably assume that if you are scanned, your full-color and naked images along with personal identifying information will be stored by Federal agencies in perpetuity.

EVEN DHS HEAD REFUSES BODY SCANNER

"Department of Homeland Security Secretary Janet Napolitano yesterday hailed them as an important breakthrough for airport security and the fight against terrorism."

"Yet when it came to testing the devices - which produce chalky, naked X-ray images of passengers - she turned the floor over to some brave volunteers." [11]

OPT-OUTS MAY NOT LAST

In the U.K., whole-body scanners have been mandatory for some time. This may well come to the U.S.

So, you will be forced to be scanned, after which you may be groped anyway, then groped again at the gate, and your images both clothed and naked will be in the bowels of a government database, which then gets turned over to various private industry bidders, who all will have a copy of all your information.

Some scanners take images in real-time at a decent framerate, which means your 3D biometric information of every part of your body will soon be recorded forever and used in any number of ways.

[1] http://www.ncdsv.org/images/SexualAssaultStatistics.pdf

[2] http://www.news.com.au/travel/news/naked-scanners-may-increa...

[3] http://www.telegraph.co.uk/travel/travelnews/7862265/Airport...

[4] http://www.dailymail.co.uk/health/article-1290527/Airport-bo...

[5] http://travel.usatoday.com/flights/post/2010/07/full-body-sc...

[6] http://epic.org/2010/01/update---epic-posts-tsa-docume.html

[7] http://news.cnet.com/8301-31921_3-20012583-281.html?part=rss...

[8] http://news.travel.aol.com/2010/10/29/tsa-launches-enhanced-...

[9] http://www.management.travel/news.php?cid=body-scans-body-sc...

[10] http://www.wired.com/dangerroom/tag/backscatter-x-ray/

[11] http://www.nydailynews.com/ny_local/2010/10/22/2010-10-22_bo...

[12] http://www.consumertraveler.com/today/no-birthdate-no-ticket...

[13] http://www.flyertalk.com/forum/travel-safety-security/114134...

[14] http://www.flyertalk.com/forum/travel-safety-security/341574...

[15] http://www.theatlantic.com/national/archive/2010/10/for-the-...

[16] http://www.reddit.com/r/AskReddit/comments/dyrr8/help_i_beli...