Just as with DRM, you cant win with a concept of wanting to control content on a platform that is not 101% locked down.
Browsers are not locked down.
The best advertisers can hope for is that users are too lazy to block. Or they can be smart and provide "ads" that provide some kind of value like contextual search result etc.
The only way that happens is that somebody figures out how to deliver the same quality of advertising at a much lower price point (perhaps a company that isn't employing quite so many PhDs or bankrolling so many moon shots). Or alternatively, somebody comes up with a much higher quality product. Frankly neither of those seem particularly out of reach.
Remember what happened to Myspace. Ad revenue started to drop, ad density was increased to compensate, users became fed up and left, company went into a screaming dive and was sold cheaply. Who's in that position now? Twitter? Facebook? Pinterest?
We're probably closer to "peak social" than "peak search".
It really isn't hard to detect. If an asset didn't go through, it was probably blocked. You're already starting to see with Hulu.
But free services and websites ( you know the stuff that's supposed to be ad supported) typically value user traffic over ad revenue. Especially if they're still in the growing phase, or if there's lots of easy alternatives to your service (the case of YouTube). They wouldn't want to risk you hopping over to another service.