In fact, the Wikipedia page about his group of thugs, in English, now specifically points out that the Italian version has been altered because of Data Protection Laws.
http://en.wikipedia.org/wiki/B...
That means only the most incompetent pedos aren't already randomly tweaking their jpgs - the smart ones are doing it in the EXIF section so it won't even change the picture.
The smart implementations probably hash the image payload excluding EXIF, for exactly that reason - maybe downsample and reduce the colorspace too, so trivial tweaks won't have that effect any more.
This isn't definitive research, but in the early days of G+, some friends posted a lot of porn to see how quickly Google caught and deleted the pictures. What they found was that Google's algorithms, once trained with a picture, could find that picture if it had been resized, flipped along the vertical axis, and cropped. (one was cropped to the point where it was no longer technically porn, since it was just a person's face, and it still disappeared.)
Living on Earth may be expensive, but it includes an annual free trip around the Sun.