Hmm... Since when is MAC address visible outside of the local network? No one but your ISP can see the MAC address of your PC or router. Unless the client itself gathers and sends information about the hardware... But in this case this data is unreliable - for instance, some ISPs charge additional fees for every PC in the household and if you want to save money you can just clone one MAC over all PCs in the house, so for ISP (and for EU client, if it really gathers information) they'll all look the same. Of course only one of those can be online at the same time, but if you're ok with that or really need to save that badly, that's the way to go. It would probably break ISP's rules but surely not MA's.