EEPW we've never piggybacked or let anyone use ours but I agree with all you say. We pay for Netflix and Amazon but fucked Sky off a couple of years ago for IPTV and loved it.
If I were to choose a new legit streaming service I wouldn't choose Netflix anyway. Probs Apple and pair with Freeview and Amazon.
How will they police mobile device use anyway? By it's very nature it's not designed to be used at the same IP address.