A little known fact is that neither your personal auto insurance nor your credit card cover you for all property damage you cause to a rental car.  All the rental companies mandate that the renter be responsible for the "depreciated value" if there is damage to the rented vehicle.  Your insurance only pays for the costs of repair.  If the rental company decides not to repair and instead sells at auction for a depreciated amount, you will be personally responsible for the difference between the sale price and the repair costs which your carrier will pay.  The difference can amount to thousands of dollars.

The solution is to take the collusion waiver.  It costs an extra 10-20 dollars per day but, I think, is well worth it.  J. Michael