Personally I can't believe how many people will leave after dinging someones car, and i'm not talking a small rub that left a mark where they might not have noticed.
I ding'd a car in a parking lot last weekend
(one of my buddies convinced me to try and park my truck in a single spot, epic fail), left my card and when the guy called, he told me he said he was suprised I left him a note because it's happened to him in the past and they just disappeared.
Then of course earlier this week i noticed that someone had hit the back end of my truck and ding'd it, now its small and didn't break the paint but i noticed it from over 50 feet away, hard to imagine someone didn't notice they did that.
But geez take some responsibility, yeah i know more then anyone it sucks, but it sucks more when it happens to you and the culprit disappears.