I don’t think Google is “unhappy about the fact that for about one-third of the search hits go to Wikipedia articles”. Google is an agent providing links to other sources of information. If Wikipedia were not in Google users would rather sooner than later go and search Wikipedia directly. They would “google” in Wikipedia, then, having gone lost for Google adverts altogether.
So, it is right to say that there has grown a kind of symbiosis between Google and Wikipedia, the latter providing the content while the former is guiding users the way.
Wikipedia articles are ranking very high in Google no matter their quality (a search engine cannot check whether what is said in an article is correct). If a term is in Wikipedia the link there will certainly be ranked among the top ten in Google. This is a decision that was taken by Google sometime. Wikipedia ever since belongs to the Google SERPs just as much as links to Google’s own products Google News, Photos, and YouTube, no matter if you indicated you were looking for news, pictures, or videos at all.
Also, please think about the financial support by Google for Wikipedia in terms of rather impressive donations.
Comment, in: Ziko’s Blog, Wikipedia and the World, 15 December 2010.