It depends in which country you rented the car. I rent all the time in the US, and havge never had a single problem being charged for very minor dents.

Colombia and other foreign countries are very different. Before you take the car out in Colombia, bith you and the rental agent do a full inspection of the vehicle and denote EVERY ding, no matter how minor - even small dents in the bumper.

On one of my rentals (in Colombia) the agent met me at the airport as I was departing to pick up the car (standard practice). I absolutely did not damage the car in anyway, nor did he say anything upon picking up the car, but a week later the charge on my AMEX was $300 more than it should have been.

I called the agent, he told me he found a scratch, therefore he put through the additional charge. I told him there was no scratch and he was not authorized to charge my card.

AMEX agreed with me and reversed the charge two weeks later.