I have noticed that on a page in my site, one of the coop links was about Xbox mods. It seems Adsense had a "love at first site" moment for those two keywords and decided to fill two 728x90 banners with xbox ads on a page that had nothing to do with xbox or consoles, mods and so on. Therefore I have decided to do this : print "<!- google_ad_section_start(weight=ignore) ->\n"; echo $ad_network; print "<!- google_ad_section_end ->\n"; PHP: Adsense now skips the links and content matching works as before, ok. If this is against coop rules, let me know and I'll have to consider if I keep the links or not, because they were really messing the ads. I don't see how it would hurt the coop system. I guess search engines will still find the links, only Adsense will ignore them.
I've found in the past that happens if you add the coop before the content with adsense. Or you do not have enough content. Adsense keys in on outgoing links. They seem to assume they are competitive ads, or in fact know, and use that topic in many instances I have seen. EDIT OK, I missed the ignore tags. DOH! Was there a crawl before them? You could wait a week or two for it to change.
The page was definately crawled before and the coop links are in the footer, after all the content. The adsense ads were pretty matched to the content. At a refresh, the coop link about xbox appeared and everything went wrong. The site I'm talking about is in my profile, the page I mentioned is the first page of the first tutorial mentioned on the site.
YPN works only in US at the moment, unfortunately. I wouldnt hesitate to use both, alternating them on pages.