Coinhive seems pretty upfront with this though (to answer "Will this work on my site?": "Technically yes, economically probably not. If you run a blog that get

Coinhive seems pretty upfront with this though (to answer "Will this work on my site?": "Technically yes, economically probably not. If you run a blog that gets 10 visits/day, the payout will be miniscule. For the captcha and shortlinks with a sensible hash goal (1024–16384) you'll need to have a whole lot of users to make this worthwhile." I do like it as an accessibility friendly captcha system, though.