Re: Of course you can backlist the domains..
"Yep. Facebook, Twitter , Amazon etc are all blacklisted here."
One of the things I rather quickly discovered in the early 1990s when attempting to block URLs and domains via a squid proxy is the plethora of domain names that pop up as alternates.
I think we gave up trying to stop students accessing penthouse.com when we got up to 1500 domain names which went to the same website - it's about then that the realisation that technical solutions to sociological problems either don't work or end up being walnut-crushing 40 tonne steam hammers that block far more than intended.