clunckdriver I totally agree.
Once, landing at Munich in an RJ100 as we came off the runway the guy sitting next to me popped open his seatbelt with a leisurely sigh. After asking him if he knew that, if we stopped suddenly, he would probably knock out the guy in front and break his own neck, his only answer was "Ja, but how often does that happen?!"
It's one of the few things that makes me angry when I think about it, years later. There's no excuse for putting others at risk. I just wish I'd known a better way to get him to see that.