By Vincent Granville, May 28, 2011
If you have more than 100 friends on Facebook, you've probably noticed that Facebook always show up the same 20 friends on your profile page, day after day. FB actually shows up to 10 friends, but they rotate from a list of 20 friends that, according to FB data mining algorithms, are deemed to be your best friends.
What makes a connection become one of your FB best friend is how frequently she visits your profile. Your can influence this list to some extent, by posting comments and likes on friends that do not show up in your "20 best FB friends" list. As you tend to visit more frequently profiles from friends listed on your profile page, your FB friend list becomes a small, immutable set of 20 people. In short, the FB algorithm get stuck in a local optimum, with no way out. You get assigned to 20 faithful friends for your entire FB life, and it's get very difficult if not impossible to change this top friendlist.
Today, I noticed that FB is experimenting: every 3-4 pageviews, they will show up an alternate set of friends, hoping that it will create user activity, more pageviews, and at the end of the day, more advertising revenue.