In the latest video by Google’s Matt Cutts, he talks about how Google may determine the quality of a page of content without there being many links.
By Matt’s expression, he seemed to give off the feeling that without links, it is really hard for Google to determine the quality of the page. He said, you have to go to pre-Google days, how search engines worked before links, and look at the words on the page.
Matt explained you need to judge the content based on the words on the page and the more often the words are on the page, in a diminishing scales type of way, the more likely the page is about that word.
Google also uses a factor to see if the domain itself has value, but that brings in links.
Without links, Google simply needs to look at the quality of the content on the page, which may or may not be enough depending on the competitive nature of the keyword phrase.