I tend to make sure people wear their seatbelts too. I'm glad the non-wearer had to pay though and not the driver!
Have you seen that advert where the person in the back who isn't wearing the seatbelt causes the person in the front to be killed?
Actually, I'm thinking about it now and it should be the driver who got fined, and then in future s/he would make sure the passengers wore their belts. If just the non-wearer got fined, they'd probably just plan on the probability that they're not going to get done for the same thing too frequently, but if there's someone else involved then there're the chance of some persuasion happening.