What these DNS-based unblocking services do is to selectively point certain hostnames to their own IPs, where they run TCP tunnels to the actual service.
It sounds like it'd be very easy for Netflix to put a stop to this - they just need to make their webpage / app / whatever check the IP their certain hostnames lookup to and if it's not the whitelisted addresses it refuses to work.
Or (much simpler) use actual IPs rather than hostnames. They can still dynamically change the IPs at will by updating their web code, so it's not hugely worse than using hostnames.
Or (much simpler) use actual IPs rather than hostnames. They can still dynamically change the IPs at will by updating their web code, so it's not hugely worse than using hostnames.