Originally Posted by
jzweighaft
Cars are not hotel rooms though. For a hotel usually it says that space is guaranteed for your reservation. That's not the case with airline tickets (they overbook seats all the time); I haven't read all the T&Cs, but I believe Hertz (and other car rental agencies) can overbook cars too.
One problem car rental companies have that airlines don't is that customers don't always return cars on time. So overbooking is not the only reason cars aren't available. From what I have read, in some jurisdictions, hotels can't easily kick out guests staying past their reservation as long as they are paying, so a similar situation can exist there too.