It is sadly quite possible to get things through the xray machine... all it takes is forgetfulness on your part when packing carry-on, and inattentiveness on the part of the operator. Now, I didn't count on it happening a second time on the same trip, and sent the offending item home by USPS, but uh, yeah.
I'm all for security in airports - and I'm not even particularly bothered by the idea of naked pictures floating around - but I am completely uninterested in a security blanket. If stuff slips through so easily by accident, how hard can it be for a determined person? :(