Walt Mossberg describes The real trouble with web ads
I agree with all of this, but I think there's another reason users might want an easy way to expunge browser ads: They represent both an unwanted intrusion and a broken promise. They are, in effect, a form of spyware, scooping up information about what people do online without their knowledge and permission, supposedly in return for useful, personalized ads.
The trouble is twofold: users can't easily opt out of the spying and tracking that goes along with these ads, even if they don't mind ads themselves. And the promised personalization of ads is, at best, crude, and often useless — except in search-results pages, which provide immediate context.
In my experience, this bargain — give us your personal information and we'll give you really useful ads, tailored to you — has simply never materialized, going back to its earliest days on desktops.
The answer is for the ad industry to reform itself, so people don't turn to ad blockers. Ads need to be less intrusive, less burdensome, and smarter. Tracking needs to be more transparent, and more under the user's control. And this reform should start now, when ad blockers are still used by a small minority of users.
I agree with this wholeheartedly.