It is a non scalable model. The more people who use this the greater the rating for mining. Currently it takes 5.5 billion hashes to meet the min payment for coinhive. At full power you might get 30h/s per person on a desktop or 15h/s on a phone. If you had 10000 mobile visitors who came everyday and stayed 1 minute it would take 10000 days to get min payout: 1/2 a monero coin so about 40/50 dollars. I don't see how this will replace advertising where one affilate sale could replace this income.