Bill Slawski has an excellent post at Cre8asite Forums he named It's all about the signals, What the Search Engines Look For. You can tell by this thread that he was really inspired by the SES San Jose event just a couple weeks ago. What is Bill telling us?
I do think that search engines still place a lot of reliance on links, but am convinced that understanding user queries - like seen in our thread on the AOL data, is playing a larger and more important role in determining relevance. There have been a number of mentions in recent white papers and patents which mention search engines collecting information from ISPs about user behavior.
Bill explains what he believes is the tracking and understanding the search engines grasp from a users click pattern and "traffic flow." It "shows how some sites are more popular than others and are attracting traffic in response to searches and other methods of getting people to a site."
In discussion forum class, Bill ends his post prompting more discussion. He asks,
What signals do you think are becoming more important, and how are you taking advantage of being within an information stream?
Forum discussion at Cre8asite Forums.