Relying on PageRank (or the graph structure of the pages) alone is no longer enough. Now you need to follow users and see who's clicking on what, and what trails are being blazed across the web. This is where Facebook's "Like button" comes in, or Google Analytics (or AdSense). Google can follow people around and see what's hot <i>right now</i>, and surface those links. WikiPedia may be a great hub, but if people are making a beeline for a Brad Pitt article on TMZ, then that Brad Pitt article may be more relevant right now than his Wikipedia page.<p>TL;DR: Search is hard. Google and others have taken ranking to levels <i>far</i> higher than PageRank, which is nearly 20 years old now.