I don't think something like this is fair at all.
Let me go into detail:
Some Blockland user, let's call him
User X, has been added to the blacklist.
User X gets on Blockland, goes to the server browser, and gets himself ready to have some fun. "Oops, I was banned? That's weird." Much to the
User X's surprise, he has been banned from ___% of Blockland servers, but why? Well it turns out that he has had some bad history with
User Y and
User Y nominated
User X to be on this unofficial blacklist. In the end
User X has been banned from so many servers just because
User Y didn't like him. These bans are permanent, so even if
User X did deserve the ban (in the eyes of whoever added his name to their blacklist) he'll never be able to join some servers ever again, even if he changes his ways.