I wear my seatbelt always...my former GF got me in the habit.
Before that I only wore it occasionally.
I understand the importance of seatbelts, but I have been in 3 accidents where I was the passenger...all 3 times I was not wearing a seatbelt, and survived without a scratch. Mostly I was just lucky though.
The first accident, I was a little kid and we were in a car that didn't even have seatbelts. A semi ran a stop sign and plowed into the car we were in nearly head on. My mom layed down in front of me and protected me. Her face hit the dashboard and she still has some pretty nasty scars from it.
The second one I was driving with a friend who rear ended another car that stopped too quickly in front of him...we were probably going about 30mph when we hit. I saw it coming and braced myself.
The third one I was driving with my uncle, my aunt (his sister) and I were visiting him and he was pretty excited, so he was talking to us and not paying much attention to his driving, he went through a red light, and the van that hit us was speeding, so while we were only going about 20, they were going 45. The car spun around and did about a 180, but again I braced myself and held on for dear life...was completely unhurt.