Depending on the payoff scale, a TDT agent will cooperate if it believes that the other agent has some (high enough) chance of being a TDT agent. In other words, raise the sanity waterline high enough, and TDT cooperates.
TDT / superrationality will defect probabilistically given a high enough payoff for defection, even against a known-TDT agent.
In short: TDT and superrationality theories aren't as simple as some here make them out to be, and the one-shot prisoner's dilemma has hidden depths for smart players.
Of course, the rational thing to do is to convince everyone ELSE to be "superrational", and convince them that you are ALSO "superrational", and then defect if you actually play a prisoner's dilemma for sufficiently high stakes.
Eliezer has done a good job of this. Hofstadter too. Inventing the term "superrationality" for "magicalthinking" was a good move.
It's a brilliant idea: a lecture by a cool modern thinker, illustrated by word-by-word doodles on a whiteboard. Excellent at pulling you along the train of thought and absolutely disallowing boredom.
The lectures' content is pretty great too, although there's a definite left-wing, populist bent that's exploting today's post-crisis hot button issues (they got Zizek, for god's sake) - some might not like it. Regardless, it's all very amusing and enlightening. Been linked to before in a comment or to, but it deserves a headline.
You can start here: http://www.youtube.com/watch?v=dFs9WO2B8uI&feature=relmfu (But they're all worth watching!)