I think the problem lies in the amount of uninformed experimentation in a given time period and how it effects the individual.
To some people, a barking dog at night is mental torture, or shining a light in someone's house really bothers them. Others can easily ignore lights and dogs and have a great night's sleep. It becomes an issue when a single individual who is bothered by it has to deal with 4 constant lights, 12 constantly barking dogs, and 1 person following you around scratching their nails on a chalk board all day (Got the phone app?). None of these sites bother to ask if anything bothers the user before testing it on them. Imagine the shittiest day you ever had, relative(s) died, lost that business deal, divorced all on the same day and say you also sat on your cat and smushed it.
You sit in front of Facebook and it starts reciting, "Nevermoore!" you might want to kill yourself, and Facebook would have been the last straw.
People don't expect such behavior from websites, because they misrepresent themselves. They keep these interactions as secrets, even porn sites have the decency to ask you, "Do you like man on man action?" before shoving a dong picture in front of your face.