The Stanford Prison Experiment

I had come across this before, but Damn Interesting brought this back. In 1971, an experiment was conducted at Stanford where 24 students were put into a prison scenario where some were guards and some became prisoners. Within a week the experiment had to be ended because the scenario became too real -- including abuse by the "guards" and the prisoners showing increasing signs of being mentally unstable.

All of this is also interesting in light of the Abu Ghraib atrocity.