Some people want to make their stuff freely available to people, but don't want it to be used to train AI. That's the group my comment was talking about. No monopolistic megalomaniacs here.
Personally, I think that such efforts are pointless -- all it takes is one crawler to make it through your defenses and you may as well have not done a thing. The alternative, though, is to remove your sites from the open web entirely. Either way, Commmon Crawl needs to be excluded if you want to avoid your stuff being used to train AI.
