We've gone beyond the Drake equation, it's coming to life...We are at 552 extra solar planets confirmed and counting. At least 2-3 of these may harbor a planet in the "Goldilocks" zone. 10% around stars like our own. Kepler may have discovered 1200 more already. 54 in the habitable zone. There are 100 to 400 BILLION stars in the galaxy alone...up to possibly 50 billion planets! We have evidence of ONE life bearing planet so far. The odds would seem to be against there not being any other sentient life in the universe.
RAMA
Indeed.... While not proven empirically (and possibly may not ever be), I'd say it's more or less a foregone conclusion that life exists SOMEWHERE else, and chances are good that even INTELLIGENT life exists out there, as well... yeah, it may not exist out there, but there's really nothing special or unique in our makeup that makes Earth the only place in all the zillions of planets and star systems that life could have possibly occurred. And that's just talking about Carbon-based life. Who knows what other permutations on intelligence or natural selection could exist out there that we wouldn't even recognize with what we currently know? Different size or timescales, perhaps? The possible existence of alien life/intelligence isn't a crackpot notion like moon hoaxing or holocaust denial.
That being said, the idea that said life has managed to travel all the way out here to probe rednecks in the boondocks... now that's crazy... I mean, we've borne witness to the difficulty of detecting life on other worlds... think about it, how would a society be able to detect US? Radio signals don't travel that far (last I heard, our broadcast transmissions get washed away by galactic background noise as soon as it leaves the heliopause). Our planet doesn't look significantly different from before we evolved on it. An alien civilization might be able to deduce that life arose here due to atmospheric analysis, but they would never be able to guess OUR existence... we're just too small... and if aliens are anything like us, I can't imagine them spending the doubtless exorbitant amount of resources necessary just to check out the possible microbial life on this insignificant planet. Robot probes, maybe, if the civilization is old and technically proficient enough, but surely, they'll be a remote probe, and not something that would reach the surface and collect samples... that's just not practical for a long range probe. Data is much more compact and easier to transport than physical specimens.
In other words, if anyone ever did fine out about us, we'll never know it.