I finally realized how insurance companies make money

Where I live, state law requires car drivers to have, at a minimum, liability insurance. This means that the insurance company will handle paying for damages you cause (up to a certain amount, exclusions apply, etc) if you cause an accident.

One night while turning through an intersection, the car next to me crossed the line and grazed the side of my car. I thought it was pretty obvious whose fault it was, and continued through the intersection to pull over by the sidewalk.  There were no witnesses. We exchanged information and went our separate ways. My insurance company talks with me and I tell them how the other driver grazed the side of my car.  The other guys' insurance company calls me up and tells me I was at fault. Net result? My insurance company and his insurance company both just deny each others' claim.

Lessons learned:

• As soon as safely possible, stop the car in order to get evidence.  Take pictures of the cars where they are, even if it's in the middle of the intersection.  Don't feel pressured to move cars out of the way to unblock traffic, until you have satisfactorily gathered any evidence you need.  In my situation, a solid white line divided the two left turn lanes we were using.  I could have taken pictures of the cars with him obviously over the line.
• If it was their fault, don't assume the other party will understand it was their fault. Heck, consider the possibility the other party would lie in order to screw you over. In general, you don't need to make it more confrontational by accusing the other party.

Who wins?

• I get a couple of scratches on my car.
• I get no payment from my insurance company.
• He gets a few scratches on his car.
• I don't know what he gets from his insurance.  If he also has only liability insurance, then presumably he also gets nothing.
• The insurance companies continue to collect money from their customers.

Fun fact: one of the insurance companies mentioned here is Geico. The premiums that drivers pay to Geico are used to finance investments in other companies, which have been used to build up a large financial conglomerate and has resulted in one of the wealthiest persons in the world: Warren Buffet.