My biggest fear would be that something happened to it while it was in my possession!!!! Especially since I am renting, I probably I would not be able to pay for that.
Of course I would care for it like my own baby. But you just never know when something crazy will happen. And then you will have no bag, have wasted your rental money on it, and still have to buy the bag!! I think that fear alone will keep me from "renting".