I also want to pin out the Topic here (and I admit that I stole it form the German version of this video from @frathiemann, so : all props to him!)
I would also prefer to mine for a sites service that to watch all these endless comercials. At least when these sites tell me what they are doing, or even better would be the offer:
"You could turn off this comercial, when you use our miner!"
When I watch a video I would definetly stay on the site, at least for the length of the video.
Questions is if the uploader can make enough money out of that.