I think Axelrod actually claimed loudly that tit-for-tat wasn't optimal, and offered a few other strategies that would have done better (including tit-for-two-t

I think Axelrod actually claimed loudly that tit-for-tat wasn't optimal, and offered a few other strategies that would have done better (including tit-for-two-tats, interestingly enough). He was also pretty careful to add that a lot depends on context and that the aspects that tit-for-tat embodies (being nice, reciprocal/retributive, forgiving, and clear) are what's really important.