Ghosts of Ghosts??

Alot of paranormal activity in recent years have bee claims of "Shadow People" these are usually described as outlines of human beings that are pitch black. One idea is that these are ghosts that have not got enough energy to appear in a complete human form so are kind of in a limbo.

I describe these shadow people as ghosts of ghosts as they have not completly manifested themselves.

Feel free to give me your opinions