The whole alien thing always annoys me, just from the basic idea that there'd be a reason for them to come in the first place. I think there is probably other life in the universe. If we've learned anything from extremophiles it's that life, if given ANY sort of chance whatsoever, manages to find a way. That said, if there was life anywhere else in the universe, probably it would be almost nothing like us. It's very possible that we could encounter other sentient life and not be able to tell that it was sentient because it interacted with the world in a completely different way than we did, and that same sentient life, if it ever found us, would have a damn hard time figuring out what we were. What's more, from a resource perspective, space travel is incredibly expensive and time consuming. Why would anyone come here? Let's say a space-faring race saw our planet through a telescope. Now... it'd probably be fairly far away from us. The closest star to ours is Proxima Centurai, and we're pretty sure there's no life there. In fact, most of the stars we have been able to see in our galaxy wouldn't be able to support life that was anything like us, so if there's any sort of life there, they'd see our planet and star and probably conclude that life couldn't exist here. They probably wouldn't be able to see any traces of our civilization. Radiowaves eventually do dissipate, so it's not really true that in a thousand years a civilization a thousand light years from us will see The OC. What's more shooting out radio-waves is fairly inefficient, a race that could actually travel through space would probably have created better technology that transmitted information better, like we do now with fiber-optics. So it's not terribly likely that they'd have out antennas to capture the radio-waves that probably can't get out there.
I have strong doubts that there is other intelligent life within one hundred light-years of our planet. That would mean that any other intelligent life, if they managed to look in our direction and see the tiny planet going around the tiny sun would see us anything more advanced than just post industrial revolution.
I think if we found other life, we'd do everything we could to make the trip out to see it. I bet that's the same as other life. But there'd be no point in taking our resources, chemically speaking we don't have anything special here. And I must assume that any civilization that has mastered space travel has a much better grasp of chemistry than we do and can take basic chemical compounds found throughout the universe and turn them into what that civilization likes. It's unlikely that they'd have evolved to live on a planet like ours, so colonization wouldn't make much sense. And I find it highly unlikely that there's anyone close enough to us to actually look at us and see signs of sentient life.
I would love to find out that there was other life out there, but I have severe doubts that we will actually find any in my lifetime.
