The question of whether there is intelligent life out there in the universe would seem to boil down to whether or not you consider yourself to be intelligent.
Based on a plug from the Professor I picked up Marcus Chown's The Never Ending Days of Being Dead in Foyles and read the first chapter: Elvis Lives.
In it Chown argues that if you accept the premises of quantum theory and inflation (a key part of the standard cosmological model), then you must accept that there is a being identical to you at a fairly predictable distance from your current location. Additionally, there may also be another identical you at an altogether unpredictable distance, the doppelgänger resulting from the many worlds interpretation of quantum theory.
And this is what is interesting to me about the current state of such parallel universe hypotheses, that there can be two absolutely identical individuals doing identical things, differing only in the theoretical reason for their being there in the first place.
I have a couple of issues with Chown's logic, which maybe someone better versed in such matters can help clear up for me:
1) Is "to all intents and purposes infinite" really the same thing as infinite? This seems quite crucial because the relative nature of the first type of infinity might prevent it from driving the rest of Chown's argument.
2) If there is a finite number of ways of arranging matter in an "infinite" bubble-universe, will all possible instances inevitably occur?
I had a similar quibble with Richard Dawkins's assertion in The God Delusion that there must be a version of me with green hair somewhere 'out there'. Maybe I'm wrong, but I think the number of possible events that are realised in practice will be constrained by the number of possible histories that follow from the starting conditions.