if the security officials had done their job correctly then the attempt would have been foiled without need of scanners, and anyway, security measures nowadays are so tight in the first place that any would be bomber can only resort to devices that don't really cause much harm and that are clearly not enough to blow up airplanes, notice how the passengers were the ones who subdued the last attempt, and that it wasn't going to work anyway., which leads to the question of how marginal the benefit would be from the scanners as opposed to officials actually doing their job correctly?
the scanners themselves pose no problem if certain safeguards were in place, such as blurring the faces for example, and the images being deleted right away after being checked plus the operator being in a separate room so he wouldn't be able to see who was being scanned etc. but the point is, they're not going to be that effective against current threats to the extent that they're toted to be.
hence they'd be a huge waste of money, a great cause of discomfort for many people as well as have a potentially negative impact on security by imparting confidence in the safety of airplanes and so on but not actually addressing the threat more meaningfully.
in fact, there's speculation on whether the Christmas attack perpetrator would been detected
at all using the scanners ...
http://www.independent.co.uk/news/w...sure-to-sack-intelligence-chiefs-1859947.html