I think keying someone's car is probably one of the lowest things you can do. Most of the time these people have no idea who you are, what you do, or how much the car means to you. It's a quick and easy way of being a horrible individual and ruin something expensive of someone else's
If someone was to key my car, I honestly think I would cry. I inherited it from my Grandad last year and it means the world to me.
I think it's a horrible, horrible thing to do.