Prisoner Dilemma: Tit for Tat or Suicide Bombing?

As described in this article, the latest prisoner dilemma competition (game theory is very cool) was won not by the usually 'tit for tat' algorithm ("be nice, fair, but tough") but by a "identify your friends, collude with them, walk over everyone else" system.

This shows that, in this game theory problem at least, there is a balance and there are weaknesses. Overly-altruistic (say-civilized) are vulnerable to overly aggressive approaches; as the number of aggressors increases, cooperation gives a competitive advantage, turning the tide.

Also read this plastic article