Wow, this bumped into the AUP rather quickly
As stated above, there are many, many planets and solar systems. If you roll a hundred dice over and over again, sooner or later you will roll 100 sixes. Although it is very unlikely that a given planet will be able to sustain life, the likelihood that several planets *somewhere* will have life is, I would assume, quite high.
This also feeds into David iz Cool's post: the fact that we exist isn't really remarkable, given how many planets there are. Yes, it's very unlikely that it turned out to be *this* planet, but it's no more unlikely than any other randomly chosen planet. And if humans had appeared on other planets but not this one, then we'd be wondering at how unlikely it was that we existed on *that* planet.
Of course, the fact that there are so many planets also means that, although it's quite likely aliens exist, it's also quite likely that we'll never meet up with them because they'd live so far away, and alien races might well be extinct or barely past the amoeba stage if we actually do find them. So, yes, I believe aliens exist somewhere in the universe, but that it's unlikely they'll make an impact on us. Still, it would be fantastic if they did.
Secretary of Unknowable Knowledge for the Rock/Dink administration '08
