Yep, it was a shameless Hitchhiker's reference.

I do think that the likelihood of there NOT being life is smaller than the likelihood that we live on the only life-sustaining planet in the universe. We know that there are other G2 stars out there that are very similar to the sun, even ones as close by as Alpha Centauri A. If stars of similar composition can form, does it not make sense that planets of similar composition could also form?

Then, of course, there is (as TruthFatal has pointed out) the possibility of life so alien to us that we don't even recognize it. All in all, the chances that "we are alone" seem pretty slim.