This thread reminded me of an article that I read from Scientific American at the beginning of this year. I found this really interesting, here's an excerpt:
"The simplest and most popular cosmological model today predicts that you have a twin in a galaxy about 10 to the 10^28 meters from here. This distance is so large that it is beyond astronomical, but that does not make your doppelgänger any less real. The estimate is derived from elementary probability and does not even assume speculative modern physics, merely that space is infinite (or at least sufficiently large) in size and almost uniformly filled with matter, as observations indicate. In infinite space, even the most unlikely events must take place somewhere. There are infinitely many other inhabited planets, including not just one but infinitely many that have people with the same appearance, name and memories as you, who play out every possible permutation of your life choices."
And here's the rest:
http://www.sciam.com/article.cfm?art...880000&catID=2