Until then I continue to pay for Spotify and using adblock for the web.
On a desktop however, it could be a game changer.
I am inclined to display a popup upon entry, telling user to disable script if they are on battery or unwilling to participate in mining. There really aren't a best practice for browser mining for now, but this is my approach for the time being.
I think that currently this is issue where both sides are partially quilty. Content creators are creating "dirty tricks" to get profit from their work. On the other hand users expect to everything to be free. Users have this huge gap in their head between "free" and "so-cheap-that's-almost-free".
Just as side note: if we wouldn't need this all high-tech for converting "free users" to $. Maybe some of great minds could think how to solve real problems... instead of "How to sell next fucking Nissan".
Also just like movies and games: if it's easier to pirate content than use it legally you are already lost. I may not to want to pay for every single services by credit card but I should be able to handle this ad-network scale easily.
Edit: Removed "I think" prefix from the comment since I THINK I repeat myself.
Also in the winter, you get back some of that in heat, and in the summer, the AC has to work harder, so that is part of the equation.