I'm posting here because I just saw a Facebook campaign to raise awareness of child abuse via profile pictures and chain letters. It takes little effort, and the marginal utility seemed extremely low, but I understand now that it is actually very good at generating fuzzies. As a side effect, the fuzzies provide an incentive, and it does generate a little bit of utility, so it's not entirely a bad thing unless it causes people to fall into the "I've done my bit for the world" mindset.