Surveyed! I noticed that someone said that they cooperated on the prisoner's dilemma problem, so I'll balance the odds and tell you all that I defected. Am curious to see if this will reflect in the karma people give this comment.

Also, I wouldn't do this, but you leave the option open of someone poisoning the well and taking the survey a bunch of times to improve their chance of winning the money. Are you screening for duplicate IP addresses?