Once I was sitting behind and to the left of a small car in a traffic jam when flames started shooting out from the bottom of the car, like a fuel line fire. I GOT OUT OF MY CAR, and ran up and tapped on his window, and yelled "Your car is on fire!!" He yelled back, "F*** You!" I got back in my car, and about a minute later his car was filled with smoke, he pulled over to the shoulder and got out and danced around as it was engulfed, as I slowly drove past it, so I honked and yelled, "HEY...F*** YOU!"
I do a lot of towing and have had people point out problems that I couldn't see. The worst one I had was one guy tell me I had a trailer tire on fire. Turned out the bearing had gone out and was smoking. If I hadn't been told about it I probably would have noticed it until the tire came off.
I have been thankful for the heads ups I've gotten, so please keep it up and remember for those that give you the finger for your efforts Karma will take care of them as Nosmo has pointed out.