There has always existed the question as to whether we are alone in the universe. To this day we aren't sure if life exists outside of our isolated little biosphere, but valiant attempts have always been made to try and make our presence known to... someone, anyone.
The probability of life existing elsewhere is quite good — if you weren't aware, the universe is fairly large. Of all the stars in all the billions of billions of galaxies, the probability is not so stark that Earth is the only life-supporting system. Notable astronomers and physicists like Carl Sagan and Stephen Hawking have contributed to attempts at finding, or at least designing a search method for extra-terrestrial life, intelligent or not. The institute for the Search for Extra Terrestrial Intelligence acclaims it as "the most profound search in human history."
To date, SETI has catalogued roughly 19,000 stars - the understood landmarks for possible life - that meet conditions understood to be suitable for cultivating biology. The most promising "HabStar" thus far is Gliese 581, a stable red dwarf star about 20 light-years away. Gliese plays host to four planets that sit in the "Goldilocks orbital zone," where conditions are "just right" for biology to exist.
However, finding stable solar systems is the easiest of astronomers' challenges. Supposing Gliese did indeed support a system with a habitable planet, let alone even the lowest form of biology, we could not possibly reach a contact signal to it in less than 20 years, beginning right away. The sheer distance creates enormous lag, which makes conversations and Halo parties alike agonizingly tedious.
The great time lag is one of the considerations taken in classifying HabStars. There are thousands of others catalogued that float hundreds to thousands of light-years away, meaning that a successful exchange would be the undertaking of several centuries, the extensive beginning of which probably consisting of bleeping integers at each other. Fascinating, controversial and terrifying though it would be, it wouldn't make for good table conversation.
And it is theoretically true that if we were the ones to first receive a message, the senders would necessarily be generations more advanced than us. If we received a signal from BCV, for example, that would indicate that 26 years ago its inhabitants had the technology and savvy to reach a coded message with precision 26 light-years away. That's quite a bit more than we can say at this point.
It would be imprudent in this discussion of extra-terrestrial life to ignore the notion that perhaps it has already made contact with Earth. I've been to Roswell, and I personally think the only aliens who have ever been there are the ones who had to first get past Border Patrol. But that's only my opinion. Our communication efforts aren't all too extensive (and, really, for good and practical reasons), but we are still making reasonable attempts, to the point where it's not unfair to think if aliens have tried to make contact, we would have already picked up on it.
There's been a recent spike in public interest in some advancement made by SETI in finding HabStars. About 400 exoplanets, like the four being tracked around Gliese, have been catalogued thus far. A provocative implication tied to these new HabStars is whether humans could colonize them if and when we finally stretch the resources on Earth to their breaking point.
As interesting as I find this new frontier of astronomy, I strongly believe finding a new Earth is the last possible reason we should consider in conducting these searches. People must realize that reaching these planets would be difficult, expensive and would require decades of travel time following decades of research and preparation. Finding new planets does not make Earth disposable, and attitudes like that distract from the very real need to maintain clean, hospitable conditions here.
The question of extra-terrestrial life will always be a fair one, though, and is, in the opinion of many, always an important item to pursue, if only for the benefit of further understanding our place in the universe. It's hard to not find the topic fascinating, if only for creative speculation.
The vastness of space represents an imposing openness, a void, something that we find mysterious, and somehow alluring. There is much to be learned from astronomy, even aside from the search for life. If nothing else, the search for the intricate things in the universe at least offers us the chance to take up a bit of astronomical humility.