I'm thinking along the lines of...........
Most people study quite a bit in medical school. Some people take a break to drink, go to a club/coffeehouse/etc., while others go to SDN and get stressed out about how much everyone else claims to be studying and scoring on their boards, and then get pulled in that way. It's like a form of positive reinforcment for studying more and more and more.........
But I could be wrong. It just seems like SDN fosters the "gunner" mentality more than say, watching CSI reruns or vandalizing property!!