This document discusses using social features to optimize apps and services. It provides examples of companies like Amazon, Foursquare, Quora, Instagram, and Pinterest that have successfully used a social graph to increase sales and engagement. General tips are given such as using Facebook and Twitter, making sure share buttons work properly, and developing for mobile first. Trends mentioned include social features being added to solitary activities, social impacting the real world through companies like AirBnB, and content being consumed in short snippets.