In my day job I work in the web development arm of a publishing company, one of its titles being oriented toward chemical engineering with a website and domain name that reflects this. We run AdSense on this site and on a few pages there's not much content for ads to target by, so (I'm guessing) they end up looking at just the URL or maybe internal links, which causes all the ads to be for Che Guevara products. Sort of makes one wonder why Google doesn't use some of the data mining results they no doubt possess in order to determine some kind of best fit ad targeting based on content from related pages in the absense of useable data.
I realize that -- this wasn't a request for help. Just thoght it was amusing how awry things could go when they're not set up right.