The document summarizes Garrett Hardin's "Tragedy of the Commons" theory, which discusses how individual interests can negatively impact shared limited resources. It uses the example of multiple herdsmen grazing sheep on a common pasture. Each herdsman adds more sheep for individual benefit, but this ultimately depletes the pasture. The document applies this theory to issues on the internet like email spam, file sharing services, and dark patterns on websites that trick users. It argues users and designers must consider the common good and avoid solely pursuing self-interest to prevent degrading limited online resources and services.