http://www.slate.com/articles/technology/technology/2015/05/snapchat_s_new_business_plan_is_surprisingly_old_fashioned.html

On the surface, Facebook is about people and relationships. Peel back its skin, however, and you’ll find layer upon layer of data. Your news feed is the product of a stunningly complex ranking system that evaluates your friends’ posts on features like timeliness, relevance, and virality. Those same rankings determine which of your friends will see your own Facebook posts, and how far down they’ll have to scroll to find them. Your every move on Facebook—scroll, click, like, comment—is recorded, analyzed, and factored into the site’s inner workings.