What do you think about those people who say aliens have visited the Earth?

I personally believe in extra terrestrial life because there are so many planets and the Universe is so large which kind of suggests that we cant be alone here. That would be such a waste and as we all know nature doesnt waste anything. Now aliens visiting us can be a fact or just a method to gain publicity. But the idea of aliens visiting us doesnt sound that bad afterall. Its absolutely possible.