In my newest novel "Interview with a Psychic Assassin", I explored the nature of Greys. In it, I mentioned some thoughts about Greys, what they do, their technology, and where they might come from. The discussion, in the novel, went on for about two pages and explored the main character's experience with Greys during her military government training.
Since writing the novel, I have been asked several times about the nature of Greys. I have also received emails and posts saying that Greys are all evil, and sent links to websites that prove it. And some that say that Greys are good, and those come with links to websites that prove it too.
The thing is, looking at the evidence of our interactions with Greys throughout history, we start to see certain patterns that are replicated from culture to culture.