There is something intoxicating about filling up a hole, namely a hole that is a defined space. Any story about anything and anybody is so vast -- in fact it's limitless. How can a story ever fill up an infinite space? With no defined spaces, many will flounder, unless they can content themselves with simply writing a story, and not trying to come up with the perfect story to cover as much of the borderless space as possible. I think that's why we are not only interested in places like the so-called Area 51 -- secrecy naturally invites curiosity of course -- but also we like to imagine what could that space up. Area 51 has a defined physical location, a hole on the map in Nevada, as well as the characteristic of being military in nature. And sure enough, the existence of Area 51 is practically its own genre in literature and film. A fantasy world is infinite and gigantic, but we know Area 51 is there, and we know just enough and just too little to want to project into it, and fill that space.
A random story generator (http://www.seventhsanctum.com/generate.php?Genname=storygen):
This is a tale about camaraderie. The story is about a space cargo hauler. It starts in a solar-system-spanning imperium. The story begins with someone questioning authority and ends with somebody breaking something important. The difficulty of cross-species communications is a major issue of the story.
This is a deconstruction of a classic legend with a strong theme of overcoming obstacles and how destructive ignorance can be. The story is about a prospector who has annoyed the gods. It takes place in a city-state on our world in a magical age. The return of an ancient evil at regular cycles plays an important role in the story.
This is a mystery tale. The story is about an astronaut who is married to a performance artist. It takes place in an outpost in North Korea. The crux of the story involves hunting. The fall of the Soviet Union plays a major part in the story.
This is a city-smashing monster story. The story is about a salesperson who has a crush on an educated nun. It takes place in a magical part of our universe. The story begins with the discovery of a lost item, climaxes with a keepsake, and ends with a political conflict.