Which will work until they roll it out fully and someone counters it with some new ad blocking. Might be more complicated than current options, but it'll be there.
Oh, for sure, or maybe some statistical method that doesn't require that much processing. I don't doubt it'll work, though. Google is wasting their time and energy with this.
That's silly, they really are not wasting anything. And even if they were, the prospect of effectively countering ad block and the growing network of alternative frontends in one blow is absolutely worth a shot. They have their numbers to test out server side ads, and worst case scenario for them is basically what they already have but much harder on the other side (makers and maintainers of adblockers and alternative frontends.)
Corporate totalitarianism (and totalitarianism as a whole) doesn't produce stability by absolute power over 100% of the population, it is stable by making it hard enough for any considerable and/or effective portion of the population to be able to do anything about it.
Easy, just do it like old school MythTV commercial detection. Buffering will be annoying, though, as you'd need to load the video far enough in advance to skip.