I read this article. SURELY Avis will get news of this article and then add a new and very clear condition in their contract that bans people from using the ring. Or do they know about it and are happy?
I have seen rental company spotters on public days, located at spectating points round the circuit, as a result someone I know has now been banned from Europcar worldwide. I have also heard that they keep an eye on the main ring photo sites for their cars.