Brief summary: Dawkins demonstrates a classic "Prisoner Dilemma AI tournament". No big surprise to us today, but at the time the revelation that Tit for Tat is one of -- if not *the* -- most effective strateg(y|ies) was a surprising result. He goes on to demonstrate animals employing the Tit for Tat strategy. Assumptions of generosity, with vengefulness, appear to be strongly selected for.
For the real world anekdote, all successful businesses that i worked with seem to be tit-for-tat-ers (i never tried to screw anyone and never got screwed, and i'm pretty sure they do apply tit for tat, or else the defectors would be more common). There could be some sneaky cheaters out there, but mostly due to misplaced beliefs of shareholders that a sociopath CEO will do better than tit-for-tat CEO.
An apparent counter-example (Goldman Sachs): http://www.nytimes.com/2012/03/17/opinion/nocera-the-good-bad-and-ugly-of-capitalism.html?_r=2