UFC recently was caught running a crypto miner on their website without an opt-in or opt-out. UFC is the number one provider of MMA pay per view content.
UFC targetted users who already were paying $9.99/month for a subscription. If someone pays or not isn't really the issue, it is very unethical to run a coin miner on a website without having an option to opt-in initially and an option to opt-out freely.
UFC silently removed the coin miner with no official announcement or apology.
Coin miners typically don't produce much for site owners. Due to low return and high electricity costs, coin miners cost far more for visitors than the site operators earn.
A recent article on Torrent Freak talked about the results ThePirateBay saw with their 315 million monthly visitors. In the article they estimated around $12,000 a month from the coin miner alone.
Most sites will likely see less than $10 a month in revenue and will likely cost end users 5x that.
Original discovered by @fknmayhem
We hope, and hopefully expect, more transparency from witnesses.
This has become a common thing as cryptocurrencies rapidly rise in price and will not be stopping anytime soon.
Fortunately a good ad blocker will prevent this, unfortunately, most of the ad blockers are being paid off to whitelist garbage as it is very lucrative to do so.
If you want a customizable, effective, and unbiased ad-blocker check out ublock Origin. It is available on both Chrome and Firefox.