I'm with the great Isaac Asimov on this one:
To sum up his excellent book on the subject, even taking the most conservative estimates the probability that there is recognisably intelligent life elsewhere is virtually 1, but given the vast size of the universe, its lifespan, and the limiting factor of the speed of light the chance of two civilisations being in communicable proximity at the same time are so small they can effectively be ignored.
This can't be quoted enough. +1