Since the beginning, Facebook has incorporated birthdays into its social DNA. Part of the fun and utility of Facebook is wishing each of your friends a Happy Birthday note on their walls while rushing to the store to buy gifts for them at the last minute.
Now Facebook is (finally) including another important annual celebration into the social network’s mix: the anniversary. Facebookers that are happily (or unhappily) in a relationship or joined in holy matrimony can now go to their relationship status and add the specific day, month, and year in which they became a couple.
Facebook was originally a website for college students, so it makes sense that the company didn’t have this feature back then. Since then though, millions of married and/or committed couples have joined the service, so this is simply a natural extension of the social graph. Congratulating happy couples on their five year anniversary is just another way for Facebook to consume even more of our Internet time.