I'll admit that I'm one of those who routinely uses an ad-blocker.  (and a java-script blocker, and a flash cookie blocker, etc.)  

It's something I've put a bit of thought into, since I make a living in the telecommunications industry.  The honest truth is most of the content I find on the Internet, I wouldn't pay for - the quality is simply too low.  Paying for this via advertising is pretty much the only option open to most Internet content providers.  However, ads in general are too intrusive for me to put up with.  If online ads were static, quiet and didn't distract from the content, I'd have no problem, but there are too many that are too intrusive an annoying to put up with.  Unfortunately, an ad-blocker that only blocks the annoying ads doesn't exist.