It used to be tough to get porn. Renting an X-rated movie required sneaking into a roped-off room in the back of a video store, and eyeing a centerfold meant facing down a store clerk to buy a pornographic magazine. Now pornography is just one Google search away, and much of it is free. Age restrictions have become meaningless, too, with the advent of social media—one teenager in five has sent or posted naked pictures of themselves online, according to the National Campaign to Prevent Teen and Unplanned Pregnancy.