1. Successful social networks align with users' relational motivations like competition, excellence, curiosity, and affection. 2. These motivations can be activated through interface features like profiles, votes, badges and suggestions that incorporate elements of comparison, achievement, exploration and social connection. 3. A key to user engagement is the use of "motivational hooks" in the interface design that tap into users' relational motivations through gamification and social dynamics while also meeting functional needs.