I have always found it more reasonable to believe that Earth was not the only planet with intelligent life than believe otherwise. There seems to be a preponderance of evidence that we have been visited in the past (and more recently) many times..
In this information age where many things are shifting (in social, consciousness and spiritual levels) evidence of these facts are surfacing. With more and more people carrying around cameras on their phones, more and more sightings of unidentified occurrences in the sky are being recorded and spread by more people. News agencies are picking up on this.
Our governments are being challenged to reveal what they know. A quick search at
http://vault.fbi.gov/search?SearchableText=UFO reveals many many occurrences or at
at http://search.archives.gov/ will reveal many cases of interactions and sightings of unexplained phenomenon. It becomes more likely than not that A) the US government has had awareness of extraterrestrial presence on and around earth for awhile and B) that this has been hidden from us.