Kind of an interesting read for you Astronomical types.
http://www.foxnews.com/story/0,2933,258540,00.html
"Instead of finding a whole range, we found nearly all of the black holes are either naked or covered by a dense veil of gas," said Ryan Hickox of the Harvard-Smithsonian Center for Astrophysics. "Very few are in between, which makes us question how well we know the environment around these black holes."