I only became aware of this sort of thing within the last few days, but an acquaintance of mine said that this sort of thing has been going on since circa 2014, which kinda shocked me.
In my humble opinion, if you don't know about it (know being the key definition, here), it's invasive, underhanded, 'black hat' and thus on the same level as malware/spyware, and it should be treated as such.
I agree. It's been going on since 2011 as far as I can tell.
Knowing about it is definitely the key.
2011? That's fairly disturbing.
I wonder how many times I've unknowingly helped someone mine bitcoin or another altcoin?