At ANC a couple of weeks ago, Hertz seemed to have plenty of cars in the garage--particularly at returns--but were turning pax away at the counters (presumably, the cars in the garage were reserved already, to pax arriving on the next few flights).

One guy followed me from the rental area lobby to the desk when I dropped off my keys and said, "I'll take his car." Obviously, an argument ensued when the agent said it didn't work that way.