Bentler - 5:36 pm on Jul 28, 2010 (gmt 0)

I suspect links are weighted by actual traffic they deliver, measured via the toolbar and analytics. This moves away from a random-walk definition of PR and emphasizes a combination of user experience metrics, and the prominence of both the referring page and its link. Along this line of thinking, pages getting more traffic via links will rank better; pages that have traffic spikes will bounce up in the serps short-term, creating fresh competition to outrank older prominent pages with higher-performing new material-- but not if the older page beats it in the competition for new links and referral traffic.