As I'm sure happens to many people in astronomy, I often get asked if I "believe in UFOs". Of course, that's a tough question to answer directly, so I always break it down into what they are literally asking and what they probably actually want to know. Do I believe there are lights in the sky that are unidentified by the average person? You bet. Do I believe they are visiting alien spacecraft? Nope - at least not with the evidence currently on hand. And the other assumed question about whether or not there is life elsewhere in the universe? Almost certainly. I'm just pretty sure that those alien life forms aren't visiting earth to kidnap and mutilate our cows.
Edited to add:
About 12 hours after I posted this, Rebecca at Skepchick tweeted about this: California Store Sells Beef Jerky Reclaimed from Cows Mutilated by Aliens