They have to!....don't they?
I mean obviously the Aliens, who pretty much created (slash) guided ancient civilizations to achieve all their wondrous buildings/rituals/inventions/carvings/pictures/writing/etc, must have been visited, while they were here on Earth in their whole guiding role, by ghosts.
Surely the ethereal plan must have been crossed in the presence of the Aliens. If ghosts are going to manifest themselves to everyday "Joe Blogs" then it stands to reason that someone as important as an Alien must have witnessed a ghost.
Aren't these paranormal entities suppose to increase their activity when great change is happening? I can only think of a few things of greater change than the changes brought about by the Aliens. So the building of the spaceship docks/re-chargers (the pyramids) must have been a regular haunt-a-thon. And aren't the pyramids suppose to possess supernatural powers, like giant conductors, harnessing the interstellar charges, like mystical power stations (well, according to Nat.Geo on Austar).
I think they should kick the archiologists out and let the Ghost Hunters in (but not Most Haunted - way too much screaming and unmanly-like behaviour, GHI - just Ghost Hunters wannabes or those two american pansies who call themselves paranormal investigators and then scream at the slightlest sound). But the GH crew would obviously need more gear and more digital voice recorders (because they rock). Don't get me wrong, the K2's have their place but in conjuction with the old DVR, these two things should make for some damn fine evidence.
More to come on this subject.