Verticals and specialized sites like buildingtalk.com offer a defined industry demographic -- I doubt too many rural housewives who clip coupons would visit this site.
This blog posting, "Who clicks on ads? And what might this mean?" suggests that the people who click on Internet ads are unlikely to be the best demographic market -- lower-income rural housewives!
Obviously this posting does not take into account the fact that the advertiser can very clearly target and measure the results of their Internet advertising -- something that is much harder to do with conventional media. But it raises the question; and reality, that much advertising is indeed ineffective and wasted, and that other advertising (in conjunction with the overall business strategy) can assist in brand development -- and the comments validate this awareness. Finally, we need to consider the effectiveness and value of some of the construction industry vertical sites -- with enough content and value to truly deliver a qualified and measurable audience.