I was looking for a good deal on a rental car for one day while in Philadelphia, PA and Hertz offered a prepaid rate that was a good $20 or so cheaper than any other!  Not to mention it fit in my budget to pay for most of the car then and would leave only about $20 to pay on the day of the rental.  When my flight got into Philadelphia, I get to the Hertz counter, only to be told they will have to do a preauthorization for $200 OVER what the balance of the rental would be, so a total of $216.00!!  Well, I had not planned for that!  I knew they would do a hold, but Enterprise only holds $50! ...