alt Hacker NewsFailing to cooperate with literal clones of yourself in a prisoner's dilemma would be a spectacular failure. There's only two things that can happen with identical decision makers: they both cooperate or they both defect. So identical decision makers who know they're identical can cross off the asymmetrical entries in the payoff matrix and the decision to cooperate becomes trivial.
Ah, but what if one of your "clones" is actually the wicked and persuasive "All-Defector" in disguise? (No, really, I agree with your analysis but if you haven't read "The Quantum Thief" you might like it.)