Don't understand why some people are so against this. I'd much rather give up a slither of my CPU to help websites I use stay online than be bombarded with annoying ads that make my computer slow.
Win win imo
I think it's a great alternative to ads and a nice way to help fund sites.
The pirate bay already abused its users by covertly running a monero miner at 100 percent CPU power. If they had revealed that they wanted to move to a browser mining funded model there would be no problem.
Other sites will try the same tactics; the blocker plugin gives users control over their computer's resources and site owners an incentive to inform their user base about the benefits of browser mining. We live in the age of services such as patreon, many users who appreciate a site will help pay for it to stay active, no need to pull a fast one on users.