This worries me though. I use AdBlock and get really annoyed when using friends' machines without it. But the system won't work if too many people use AdBlock.

This worries me though. I use AdBlock and get really annoyed when using friends' machines without it. But the system won't work if too many people use AdBlock. So if more ads -> more adblock -> then what? My nightmare scenario is the spread of what already goes on on alot of less scrupulous sites: "we have detected that you are using AdBlock. Turn it off to view our content". It reminds me of the excellent dystopia-satire "Black Mirror" where citizens are forced to view ads and if they look away or shut their eyes, an increasingly loud tone is played along with a "warning"...