This is exact same quote can be used to describe half the javascript files you load on almost any given news site.Without a prompt, disclaimer, or some form of user interaction - it could be seen as a browser exploit of sorts. Imagine the returns of a large visitor base.
Again, user tracking and data mining for use in advertising. If it ever did become a widespread problem, CPU usage can easily be countered by browsers implementing resource limits on tabs, which is already ridiculously easy on some operating systems.For sure, but this converts processing power into a tangible currency. It's uniquely fit for nefarious use.
Ah, I didn't realize you were referring to other monetizable examples! Great parallels, I'm a bit ashamed I didn't pick up on them myself. To sidetrack back to my original presumption, do you have any thoughts as to why they (these tidbit developers) are being met with legal action?