While "free" does indeed cause strange behavior in people, I think both of the specific behaviors you discuss are better attributed to other causes. For Hidden

While "free" does indeed cause strange behavior in people, I think both of the specific behaviors you discuss are better attributed to other causes. For HiddenCash: People love scavenger hunts and game-like challenges, especially when there's an opportunity to beat out hundreds of other people competing for the same thing. The reasonably large sums are the reason for the press coverage and popularity of this specific set of scavenger hunts, but I think that their sustained popularity from here on out is largely independent of the value of the prize (in either case, I don't think it's going to last too much longer). That said, it's worth keeping in mind that a couple hundred bucks is a TON of money to a lot of people, and the fact that all they have to do is find it first is very appealing. For fund-raisers: It's often important to people to feel joined with a cause, and donating time can create an emotional link that donating money may not. On an unrelated note - geocaching evangelists should be milking this, they have an opportunity to attract a lot of people who have found that they enjoy scavenger hunts.