I'm not missing the point. Reverb do need to take better precautions against fraud as they're not doing it terribly well at the moment, but any notion of IP address banning is ridiculous, and your statement about not being difficult to ascertain whether an IP address corresponds with VPN, internet cafe, etc is woefully far of the mark. Your other suggestion of checking for email addresses is better. The entire transaction needs to be done within the aegis of Reverb (which needs to be watertight) with T&Cs making clear that if it isn't, you're on your own.