Facebook automatically cataloged every tiny action from its users, not just their comments and clicks but the words they typed and did not send, the posts they hovered over while scrolling and did not click, and the people’s names they searched and did not befriend. They could use that data, for instance, to figure out who your closest friends were, defining the strength of the relationship with a constantly changing number between 0 and 1 they called a “friend coefficient.” The people rated closest to 1 would always be at the top of your news feed.
