Every site that you go to nowadays will always have their most popular or their most clicked on posts and images because they want the user to click on as many of their links as is possible. The more people click on, the more ad revenue the site will gain. it's easy to track the numbers and alter the list of the most popular areas based upon this so their is no reason not to have a most popular section.
Similar to most popular is when a site puts a list of similar articles or posts to something your viewing. The more time someone spends on your website then the more money usually the site will get. Buzzfeed is very good at this type of marketing, constantly promoting their lists of images and opinions and their most popular posts which they spread crazily on facebook and twitter and reddit and other social media sites. They know their general audience and they know what that person wants to look at so they will tailor their site to each specific person almost.
