[goldemerald]

There is an ethic commitee (the IRB) at every university that reviews all academic research involving people. In order to conduct a user study, researchers are required to compensate participants fairly. The reason you can pay MTurkers "far less" is that a study may only take 5 minutes, and researchers typically pay $10/hour. People won't participate in a study unless the minimum payment is decent. I can't imagine many people would want to take the time out of their day to show up at a lab, work on a computer task for 10 minutes, and get paid $2.