I agree with Irascible 100% im also bothered by the term UFO being used for every type of alien. UFO is Unidentified Flying Object, for example a plane that nobody knows where it comes from is a UFO untill its and IFO

Extra terrestrial = aliens

But the fact that we havnt found anything yet only strengthens the theory of life in space, in my opinion. as Irascible said, theyre smart enough to hide. We are really good at killing stuff. And if we found life in space, we would pay NASA to send a-bombs or whatever to them im sure...