Before 2009, Facebook had given users a simple timeline––a never-ending stream of content generated by their friends and connections, with the newest posts at the top and the oldest ones at the bottom. This was often overwhelming in its volume, but it was an accurate reflection of what others were posting. That began to change in 2009, when Facebook offered users a way to publicly “like” posts with the click of a button. That same year, Twitter introduced something even more powerful: the “Retweet” button, which allowed users to publicly endorse a post while also sharing it with all of their followers. Facebook soon copied that innovation with its own “Share” button, which became available to smartphone users in 2012. “Like” and “Share” buttons quickly became standard features of most other platforms.Shortly after its “Like” button began to produce data about what best “engaged” its users, Facebook developed algorithms to bring each user the content most likely to generate a “like” or some other interaction, eventually including the “share” as well. Later research showed that posts that trigger emotions––especially anger at out-groups––are the most likely to be shared.
The Firehose versus the Algorithmic Feed
See related from The Internet Is Not What You Think It Is: A History, A Philosophy, A Warning, except with more depth here.