I would think the number of times someone wearing a seatbelt is seriously injured by someone not wearing one is rather small. Insurance companies lobbied to have the laws passed to lower liability payments not to prevent human missle injuries. You could argue that liability is a good enough reason to pass the law since someone else is being forced to pay for your preventable injuries but I think the threat to others argument is a little weak without some solid numbers to back it up. Preventing a few freak accidents is not enough justification to force millions of people to wear seatbelt if they do not want to. Even the liability rules can be better addressed by removing liability claims for people not wearing seat belts. That is a little tougher though and I am not sure it would hold up in court.