Teenagers can still have trouble discerning fiction from reality, particularly in groups. I knew kids in high school who were absolutely convinced they had known each other in past lives, and would tell elaborate stories of their past histories. My husband knew kids who were convinced they had multiple personalities. One of the powerful things about Slenderman is that he has no face. He is a blank canvas upon which anyone, particularly those with an overactive imagination and a shaky grasp on reality, can project their own ideas, their own darkest desires. Still, I disagree with those who might say that the stories are responsible for what happened. The idea might provide the ager, but the growth upon it is all due to the girls, and it could easily have grown on something just as sweet.