I just saw the movie Aliens, and now this thread comes up. Freaky.
Anyway, there are 700 billion stars within within five million light years of our little planet. (And that's just our litle sector, not to talk of the whole universe.) Now, even if only one tenth of those stars have planets, and they only have one planet, that's still 70 billion planets. The chances of life NOT developing are slim to none.
The chances of us making contact with anyone are also slim to none. If there is life out there, it will probably be on out technological level, unless they somehow got an evolutionary kick-start and developed into intelligent beings before we did. Anyway, even if someone discovered a way to proppel a ship at the speed of light, it would stilll take them thousands of yeasr to get anywhere, and even if they did pass through our galaxy, or even our soalr system, how do we know that they would notice us? They're probably in cold sleep or something. So the chances of space ships of any kind visitng our planet any time soon are, not to repeat myself, slim to none.
*edit*
Ok, I just read some othe rposts on this and saw that someone said something about the Fermi Paradox (If there are aliens, where are they?) Well, there aer 50 billion galaxies in the universe. I would be very surprised if anyone could find us. In my view, the Fermi Paradox is obsolete