Possibly the main and original inspiration for Yudkowsky's various musings on what advanced game theories should do (eg. cooperate in the Prisoner's Dilemma) is a set of essays penned by Douglas Hofstadter (of Godel, Escher, Bach) 1983. Unfortunately, they were not online and only available as part of a dead-tree collection. This is unfortunate. Fortunately the collection is available through the usual pirates as a scan, and I took the liberty of transcribing by hand the relevant essays with images, correcting errors, annotating with links, etc: http://www.gwern.net/docs/1985-hofstadter

The 3 essays:

1. discuss the Prisoner's dilemma, the misfortune of defection, what sort of cooperative reasoning would maximize returns in a souped-up Prisoner's dilemma, and then offers a public contest
2. then we learn the results of the contest, and a discussion of ecology and the tragedy of the commons
3. finally, Hofstadter gives an extended parable about cooperation in the face of nuclear warfare; it is fortunate for us that it applies to most existential threats as well

I hope you find them educational. I am not 100% confident of the math transcriptions since the original ebook messed some of them up; if you find any apparent mistakes or typos, please leave comments.