Picture yourself on a new site. You were bored, wandering around on StumbleUpon hoping to find something interesting when after several pages, you settled on one that looked promising. The information is really good, well written, and just what you needed. After looking around, you realize the site is huge. Hundred upon hundreds of posts await your reading. Where do you begin? You could look at the list of related posts at the bottom of the page you are on, but on the side, you see two words that catch your attention: Popular Posts.