On a more serious note, targeted ads when implemented incorrectly can lead to privacy violations by leaking information about the viewer of the ad: http://theor

On a more serious note, targeted ads when implemented incorrectly can lead to privacy violations by leaking information about the viewer of the ad: http://theory.stanford.edu/~korolova/Privacy_violations_using_microtargeted_ads.pdf http://theory.stanford.edu/~korolova/Privacy_violations_usin...