http://notch.tumblr.com/post/8208212863/the-psychology-of-the-reticle-and-the-feeling-of
Read that. Endermen are the new 'creepy' mob. They are peaceful until you look at them with your crosshairs. If you look at them with your crosshairs, they look at you. If you turn away, they attack you. They also have the ability to teleport if far enough away.
another reason to keep my game on peaceful. still hope they implement the NPC villages. the Millenair mod only does so much.