Everybody knows that AdSense looks at many factors in your site to deliver your ads, but i found out another factor AdSense looks at, and that is your achor backlinks. I have a site about cars, but one day i got a backlink from a site and they linked back to me with the anchor text "Trucks" "I don't know why" and started getting traffic from that backlink and when i saw my ads they were displaying truck ads, "I didn't change my content at all when this happened", also i don't have post about trucks only cars", so in my opinion Adsense takes to account your anchor backlinks.
I suspect that they use backlinks to help determine "the topic" of the page. Of course, in this situation Adwords got it wrong and probably resulted in lower click-through rate on the ads on your page. May be adding relevant links would help improve AdWords targeting and improve clickthroughs/revenu? Just a though.
It would be cool if adsense served ads to users based somewhat on the anchor text of the link that they followed. Surley that would be possible.