Except since life formed on Earth we know that life can form. We understand the basic chemical and energy requirements that lead to life, as we know it, and we can detect those on extra-solar planets. You're right these are guesses but they are far from uneducated. As far as the issues of having a large moon or near radiation as I said earlier we have found that life can survive in what we previously thought of as environments that couldn't support life so it's also possible that life can survive in other environments where asteroid strikes happen and there is a lot of radiation. I agree that it's probably not intelligent life but life still.
Statistically it's almost a certainty that other life has or will exist somewhere. But given the scale of space and time, with the limits on the speed that anything with any organized mass can travel and the tiny portion of the universes history that Earth humans will actually exist in, we will never know.
Don't know if anyone read the link but the incident at Edwards AFB involved six UFOs flying through restricted air space for about six hours and being picked up by 5 or 6 different military radar installations. These objects displayed "unnatural" flight characteristics and no one could identify them.
Recent scientific discoveries have scientists completely rethinking the very definition of "life". Recent discoveries such as this: http://gizmodo.com/5704158/nasa-finds-new-life If life can spring from chemical compounds on EARTH that previously had not been discovered, it completely changes the probability of life forming, and it may not be quite as hard to have an environment where life can form. The discovery of "arsenic-based" life forms has caused NASA to re-evaluate whether planets have conditions for life. The fact that our next closest planet in OUR OWN SOLAR SYSTEM is showing signs that it might have had life (Mars) at some point might actually point that life in the universe might actually not be rare at all, and in fact MIGHT be (relatively speaking) kind of common. Compound that with the sheer size and scope of the Universe, the vast solar systems that exist, etc, and you have life out there. The question to whether another life form has advanced to be able to travel or communicate outside their sphere of influence is another question entirely.
