Well, if all of the involved are aware what's going on it is of course a more direct way of paying back than ads...

I created a game where that was the monetization strategy. You accumulated dynamites in the game by doing PoW with your browser. It also worked as a bot fighting technique since it was a multiplayer game.

The income was abysmal and it never felt quite right, even though I clearly prompted the user that I would use their CPU when they clicked "Mine". Since Coinhive shut down the game no longer works but here's an article about it: https://btcmanager.com/tombs-io-launches-collaborative-onlin...