Also knocking on wood that this has not happened to me. I recall a day in MKE when the on-site lot was empty but that the rental agency was shuttling cars over from an off-site holding pen as fast as it could. I wasn't happy, but also knew I would eventually get a car.

I suppose that a savvy traveler might make 2 rental car reservations with two different agencies, but only if you know that the counters are more or less adjacent to one another. I guess if this experience becomes more the norm for me, I'll have to start thinking about risk mitigation strategies.