Interesting article in the New York Times this morning discusses how rental car companies are dealing with the downturn. In short: their cars are getting worse. Usage time for a typical car has crept closer to two years and total mileage can pass 30,000.
The reason for this is a bit counterintuitive: rental companies have to sell their old cars to make way for new ones. With the auto market in shambles, they can't move the old inventory profitably, so they can't afford (or make room for) new ones, leaving an aging auto fleet with few options.