The problem with contextual advertising is that computers don’t really understand context, they just look like they do.
The most common way this shows up is in ads that match keywords, but not the intent of the page.
For example, amazon.com’s page for
Alfie Cohen’s “Punished By Rewards: The Trouble with Gold Stars, Incentive Plans, A’s, Praise, and Other Bribes” offers these contextual ads (served by Google):
The Tools You Need For Your Next Incentive
Find Solutions for Your Business Free Reports, Info. & Registration
Personalized awards & incentives sold with our Price Guarantee.
Oh dear. These folks won’t get a very good response selling ads for incentive programs on a page for a book that is explicitly AGAINST incentives.