This quick TED talk entry is courtesy of TED.com. Infidelity is the ultimate betrayal. But does it have to be? Relationship therapist Esther Perel examines why people cheat, and unpacks why affairs are so traumatic: because they threaten our emotional security. In infidelity, she sees something unexpected â€” an expression of longing and loss. A must-watch for anyone who has ever cheated or been cheated on, or who simply wants a new framework for understanding relationships.