Floor Mats Floor Toyotas

As a frequent customer of Budget and Enterprise, I've long wondered why the hell rental cars always remove the floor mats from their cars. Toyota's recall today of 3.8 million Toyota and Lexus cars over faulty floor mats may shed some light on the mystery.
For those who haven't heard, Toyota announced the recall because the floor mats have somehow caused rapid acceleration that led in many cases to crashes, and in at least one case may have led to a family's death. According to the Detroit Free Press, one guy claims a floor mat malfunction caused his Toyota to hit speeds of over 100 mph over a six-mile cruise, which seems about right given the horsepower to weight ratio of the average Toyota.
Here at Rumblenote, we can't imagine the physics behind how a floor mat could cause acceleration, though we admit we spend as little time as possible in Toyotas. We have, however, run across the bunched up winter floor mat under the break pedal effect, which certainly makes breaking a challenge. But what we really want to know is if Budget has been looking out for us all this time, or if another reason is behind the missing mats.