The deviantART community is incredibly deep and diverse. Every day, amazing art is produced that appeals to all tastes. Our goal in sharing and exposing the deviations in deviantART's Popular section is to showcase this depth and diversity as convincingly and fairly as we can.
DeviantART's algorithm for Popular browse results is known as Fair Exposure. The goal is to maximize the display of the most popular deviations in a variety of topics (styles/genres/art forms). Fair Exposure increases the probability that someone will see something that they personally like in Popular results. In short, with Fair Exposure, the community is exposed to a varied cross-section of deviantART. It uses an algorithm that is "fair" in nature -- meaning not biased toward any topic, yet still based on popularity.
Ranking deviations based on raw popularity alone is something that deviantART hasn't done since 2008. While using raw numbers has some benefits, it also has many problems. One major issue is that it inherently favors the already popular -- making that which is popular more likely to be seen, gaining even more popularity.
Different styles and types of art appeal to different deviants, and those deviants use the Favourites system in different ways. For example, fan art enthusiasts are more likely to Favourite a deviation based on subject, whereas, fine art photography lovers are more likely to Favourite based on technique. Thus, comparing the number of Favourites on one type of a deviation to another is like comparing apples to oranges.
Fair Exposure's task is to strike a balance between showcasing depth (i.e. deviations that are popular with many individual deviants) and breadth (i.e. deviations that are popular with a wide variety of deviantART sub-communities). We do this with an algorithm, the components of which are adjusted from time to time to produce an inherently fair outcome in terms of art that would be of interest to the broadest spectrum of deviants.
Version 1.0 of Fair Exposure was launched in February 2008, and the next set of updates (2.0) came in December 2011. Fair Exposure 1.0's computation became slower and slower with every deviation added to deviantART. While it executed in a reasonable amount of time in 2008, it was no longer updating fast enough for the front page. However, Fair Exposure 2.0's computation was structured differently and was faster.
While Fair Exposure 2.0 had been in development for quite a while, some of our more sophisticated ideas weren't able to make it into the initial release. The changes in Fair Exposure 2.1, made in January 2012, are very minor -- mostly code reorganization, and a few bug fixes that addressed rare edge cases that sometimes influenced front page results. We know this new version of Fair Exposure is a better representation of the world-class art produced by the deviantART community.
We have a variety of improvements coming down the pipeline -- in particular, improvements having to do with topic "accuracy" (i.e. becoming better at detecting the topics of a deviation) and "popularity" (i.e. detecting whether a deviation is "popular" amongst a niche group or has broader appeal).
Fair Exposure 2.1 is not inherently more "random" than Fair Exposure 1.0 was. The most significant determinate of order is still in deviants' submission/viewing/Favouriting patterns in general. Similarly, all determinations of popularity are made by looking at the data, with no artificial fudge factors biasing towards one topic or away from another. In particular, it does not replace art from a "popular" deviant (or topic) with art from a randomly-selected "unpopular" deviant. Fair Exposure 2.1 explicitly attempts to select "popular" deviations that showcase as many "popular" topics as possible, whereas, in Fair Exposure 1.0, there was no explicit goal to showcase a wide variety of topics. This does mean that if, for example, a deviation that showcases "people" and "photography" is displayed, the next several deviations are unlikely to be other "people" or "photography" deviations, unless they are also extremely popular.
Changes to Fair Exposure and Popular browse are in the interest of highlighting the best from a wide range of deviants and showcasing an array of styles and genres. Keep in mind that you can always browse by your particular interest using the category tree or join a group that matches your interests. We're a large community, and with Fair Exposure 2.1, we hope to bring more deviants into the spotlight.