I tried it on a couple of sites I have with ~1k users using pretty heavily. I made $1.50 USD over a couple of months, and most complained that it was being blocked/giving security warnings when visiting the site.

Not that I am making much from ads either, but it just really wasn't worth it. Affiliate revenue, while small on a grand scheme, was much more effective .

Even at the start their rates were fairly bad, price crashes + being blocked must have made it a lot worse. And few legit sites are going to use something that gets them branded as hosting malware, even if only some of their users use software detecting it.