There are 3 websites that I know of where guys can join or simply visit the site and see they have been blacklisted. The information is public and not in a secure environment.
There is another site where a guy can signup and pay a membership fee to see if they have been blacklisted.
On the other websites, the pages are not encrypted even if a provider has to log on to access them. A simple Google search that matches information in the blacklist will show the website and perhaps any behind the scenes pages.
So many factions of retired providers starting blacklist websites have made the entire concept meaningless as far as the hobby is concerned IMO. Providers blacklisting clients and Google picking it up is doing much damage peoples personal lives and that is where the problem is.