I've talked to a few ardent believers in UFOs over this thing called the internets... And I've basically always come up with one piece of logic that basically makes them quit.

We as human beings have the technology to fly over your house fifty times a day and conduct all sorts of surveillance. We have the capacity to listen all forms of communication you conduct... And you will never know any of it is happening.

Do you seriously think an alien race with technology capable of traveling across distances of space, a level of technology that would have to make trivial faster than light travel in order to get anywhere... Is going to fly down close enough to be seen with the naked eye?

As Yakko Warner famously said... It's a great big universe.