Honestly sharing one's utility function to allow a Pareto optimum to be reached is cooperating in a prisoner's dilemma in which multiple sides say what their utility function is.
Indeed, and a it is a prisoner's dilemma in which the other person doesn't even know if you defected after the fact.
Michael Nielsen's new book Reinventing Discovery is invigorating. Here's one passage on how a small group talked an issue through and had a large impact on scientific progress: