I think the reality is that most users get very little value out of the web sites and apps they use and would be just as happy to not use them if they disappeared due to low ad revenue. For those that they would actually miss, some large percentage might be willing to pay for them.
In fact, Hulu [1] just announced that they are no longer offering an ad-supported version. That's pretty telling. Either their service was so bad that they couldn't even give it away (doubtful given that they've kept the paid version), or users actually do hate ads and are willing to pay for content that's actually good.