That's great, but his list is a list of proxy servers. The purpose of those proxy servers is 'proxy avoidance'. My content filtering automatically filters pages in the category of 'proxy avoidance'.
Therefore, if someone wanted to use his proxy servers (which he's constantly adding new domains to to get around my attempts to keep my employees from avoiding my filters) he needs a way to get them those proxy servers and they need a way to find him. I'm not allowed to block email services, but I am allowed to block sites related to getting around my filters.
This is why email works better. They can sign up at home or on some page before I find and block it, confirm via email, then get updates even if I'm blocking the place where they signed up in the first place.
There is a problem with emails being blocked as well, but that is spam filtering not my active attempt to keep them from getting around my filters. Overall this is the fundamental problem with getting around content blocking/filtering. You have to be able to find the site that tells you how to get around the filtering before the people doing the filtering filter that site.