I rent a lot of cars. Last year, I got two claims against me. One was for tyre damage which I was told wouldn't be charged because it was too small on taking the car. The guy who checked it in had a different idea. (Enterprise) Successfully appealed. The second was under very strange circumstances. The check in guy found some damage which looked like it had been keyed - but wasn't there earlier in the day. He was hinting that the problem could go away there and then with a cash payment! I said no. Later I got an e-mail request to pay an astronomical figure backed up by a damage report from some dodgy garage with a photo attached - of a car with a different colour! I later got a phone call from someone asking for my card details - which I refused saying that they already had them. By this time, I was very suspicious and I told them I thought this was a scam - they put the phone down and I never heard from them again. I think this was a scam by the employees! (Sixt).
It's about time the industry got regulated.