If this came to pass and everyone started using it, wouldn't we lose many of the sites that make the web great? I don't think so. The web was great before ads were common and it'll still be great once they've retreated. There are two kinds of content on the web: content that people create and share because they have something to say and they want it to be heard, and content that people create in order to have something to put next to their adverts and make money. If all of the latter disappeared, I don't think I would miss it much. There would still be journalism, because there would still be stories that people want told (though perhaps without advertising to fund it, journalism as a career would become less common and those stories would be told directly by the people who want them told).
Arguably the twitters and facebooks of this world are more accessible than finding a hosting provider and installing WordPress or writing raw HTML. But even in the earliest days of the time I've been online I don't think there was ever a shortage of places that would host your content for free, especially if you had something interesting to say.
Even the best ad-blockers aren't perfect, though. Rather than packing up and going home, I think ad-supported content on the web will move to using adverts that computers can't tell are adverts - something more like product placement. Rather than being separate files, adverts will get integrated right into the desirable content, with no obvious computer-readable markers to demarcate them. Text, images, audio and video are all susceptible to this technique, and is starting to show up in the wild. At least these techniques don't lend themselves so well to "ad tech" - tons of scripts that bring the browser to a crawl, track all sorts of information about you and auction parts of your screen to the highest bidder. About all they'll be able to do with inline ads is tell that you've downloaded the media with the adverts in, and perhaps correlate that with a web search for the advertised product some time later - they won't be able to tell for sure that you saw the ads.
If these "inline" adverts start to become obnoxious then people will find a way to block these too - perhaps with audio fingerprinting or shared lists of timecode pairs that can be edited out. Editing is a bit more difficult for streaming content - if it's delivered "just in time" then removing it would leave an annoying gap. This could be solved the same way TiVo solved it for broadcast TV - you record for a while before you start playing your stream, then you can edit out adverts by just skipping forward in the recording (at least until you've caught up to real-time).
Ultimately I think advertising will have to be entertaining to survive as well as being non-obvious and inline. A good example I saw recently was in this episode of Comedians in Cars getting Coffee - at 4:30 Seinfeld is driving around looking for his product placement. Some of the other episodes have similar gags, and I can't see anybody going to the trouble of editing those out - they're too intrinsic to the show, too entertaining and not at all obnoxious.