There are ~100 BILLION planets in our galaxy alone, with 17 BILLION of them being earth sized: http://www.slate.com/blogs/bad_astronom ... anets.html
The odds of there being life on at least one other planet in our galaxy is, in my opinion, extremely high. The off of there being life on a planet somewhere else in the universe is even higher. Do any of them have the technology to travel here? Maybe, but I'd wager that whatever happened was from this planet.
The military has some pretty intense projects, most of which never see the light of day cause the technology deployed is unreliable or not yet fully functional. The likelihood of us being visited is slim, but there are very interesting cases.
What kills me are the people who are closed-minded and think that "WELL IF WE HAVENT DISCOVERED IT YET, IT MEANS IT DOESNT EXIST AND IS IMPOSSIBLE," this mostly regarding the technology of space travel. Advanced civilizations wouldn't need to travel the speed of light because they would most likely be capable of bending and folding space around a craft or traveling device. The arguments made by old debunkers are very archaic.