Note by @fastfinge

@Genstar @IceWolf This, too. It also feels like...one step away from cryptocurrency mining. Remember when captchas were just to tell humans and computers apart? Then they were to help digitize public domain books for the general good. Then they were to help digitize books for Google's ebook library. Now they're to help train Google's AI to recognize photos! How long until someone goes "Hey, as long as we're making someone's computer do work to prove it's a real person...hmmm...why don't we have them mine some bitcoin for us? For charity! Well, at first..."