The Ethics of Milgrim’s Obedience Study and The Stanford Prison Experiment When

The Ethics of Milgrim’s Obedience Study and The Stanford Prison Experiment
When we do research in Psychology, we need to be concerned with remaining within the boundaries of ethical considerations. Some of you might be familiar with the Milgram experiment. If not, here is a good article to read and a video replication for more background information:
http://www.psychologytoday.com/articles/200203/the-man-who-shocked-the-world (http://www.psychologytoday.com/articles/200203/the-man-who-shocked-the-world)
http://www.youtube.com/watch?v=y6GxIuljT3w (http://www.youtube.com/watch?v=y6GxIuljT3w)
Another great point of discussion for ethics and psychology is the Stanford Prison Experiment. Here is more information for you:
http://www.prisonexp.org/

Considering both the Milgram Obedience Study and the Stanford Prison Experiment, what makes an experiment ethical or unethical? More specifically, when does an experiment cross the line into being unethical? How, as a researcher, can you find and strike a balance between the good of knowledge and understanding and preserving ethics?