This document summarizes a study on the psychology of sharing and the motivations behind why people share content online. The study used ethnographies, interviews, and surveys of 2,500 regular sharers to identify six distinct personas of online sharers: Altruists, Careerists, Hipsters, Boomerangs, Connectors, and Selectives. Each persona is defined by their emotional motivations for sharing, how they want to present themselves, the role of sharing in their lives, and their preferences for sharing platforms. The study also provides guidelines for marketers to get their content shared, such as appealing to relationships between consumers and a sense of urgency, while maintaining trust and simplicity.