I haven't rented a car in years. Is it customary for Auto Europe to charge my credit card a month ahead rather than just holding the number until pick-up? I just looked at my credit card bill and I was charged a month ago when I made the reservation. (Ditto Alla Giudecca Hotel in Siracusa)
For rentals in Italy, it is the usual practice for AutoEurope charge the full amount of the rental when you book. The entire amount is refundable if you have to cancel and there is no penalty for changing dates, etc.
Different hotels have different policies about charging deposits in advance....the policy should have been specified in the booking offer or at least on the web site. The more important thing is the cancellation policy--when you can change or cancel a booking without penalty--and if they will refund the deposit in case of cancellation.