I don't think that crypto mining is going to be able to completely replace ads on websites. The javascript to run the mining code either needs to be on websites that get millions of hits or on a site that gets less hits but people staying on their for a longer period of time (or both) to make the equivalent amount of money that a website can get from showing ads.
Coin mining could easily replace ads on Facebook or Youtube even if it were run at its lowest CPU setting and still get millions of hours CPU time because of the huge numbers of users who are on these sites for hours. But for smaller sites that get most of their traffic from search engines probably wouldn't have enough people staying on there for long periods to make it profitable.
Biting the hand that feeds IT
