Aaron Wall discovered a Google Spam document that he then shared with his readers. Brian Ussery archived the entire spam recognition guide for our perusal (here) and explains that while he had initial doubts about the authenticity of the document, it looks like it has some legitimacy. He notes that relevancy isn't necessarily the most important issue. Sometimes, other concerns will impact how Google perceives your page, especially if a social networking profile is maintained by an owner. (Google considers this not just relevant but "vital".)
Barry takes the document the next step and talks about it over at Search Engine Land where he explains the three types of queries (navigational, informational, and transactional), provides details into quality rating (vital as discussed earlier, useful, relevant, not relevant, off topic), discusses the categories that cannot be factored in (can't load, foreign language, unratable), and gives us Google's spam categorizations (not spam, maybe spam, spam). There are also 2 other flags for pornographic or malicious content that Google apparently ties to pages.
While the document is dated April 2007, I don't think much has changed. The information seems incredibly useful and should be taken into account when generating content for a website (especially if Google is important to you!)