This document discusses social knowledge, which is knowledge held collectively rather than individually. It argues that social knowledge on the web has three key characteristics: [1] It is globally accessible knowledge that can input to the deliberations and actions of all web users. [2] Individuals increasingly offload and rely on social knowledge over individual knowledge. [3] Social knowledge on the web better enables the coordination of social actions as everyone accesses the same information. The semantic web may help link disparate pieces of social knowledge to form new inferences.