(Picture is of Matt Cutts, Google Engineer and unoffficial SEO-liaison)
There's an interesting story about Google called "Publishers vs. the Censorbot" making its way around the blogosphere today. In short, publishers that rely on Google AdSense for advertising revenue may being 'penalized' by Google depending on the content's subject matter - when the content contains keywords that Google deems objectionable, Google refuses to display ads next to it.
The search engine optimization (SEO) industry has been dealing with this issue for years. Should your pages work well for users or should they be optimized for search engines? Sometimes, though not always, the techniques for each strategy are mutually exclusive. Now that Google accounts for more than 60% of US searches (according to Hitwise), many e-commerce sites can attribute an even a greater percentage of their revenue to Google than previously. As the number of pages indexed bounce up and down in Google's index, so does the site revenue. Now, publishers relying on AdSense revenue are tackling similar issues and struggling for the answers.