My feeling is it is much ado about nothing - although some advertisers may be impacted more than others depending on their niche and how they advertise.

Some thoughts:

- for every person installing an ad blocker there are two other people installing adware and asking to be marketed to like the Ask Toolbar, Alexa Toolbar, etc.

- If the person is anti-ad enough to install an ad blocker they probably didn't click on ads in the first place.

- Some niches will be more "ad savvy" than others. MMO/IM niche is very banner ad savvy, same with gaming niche and technology niches.

Some businesses rely in PPC/PPV more than others. Depending on their niche and marketing strategy, they could see a tangible hit on results because of ad blockers.