Folks interested in reading more about the Prisoner's Dilemma might want to read Robert Axelrods' The Evolution of Cooperation.

http://www.amazon.com/The-Evolution-Cooperation-Revised-Edit...

He also wrote a follow-up book, The Complexity of Cooperation: Agent-Based Models of Competition and Collaboration

http://www.amazon.com/The-Complexity-Cooperation-Agent-Based...