For a found-footage-style movie, there's a definite advantage in using unknowns, because it helps sell the illusion that it's real. A known actor would get in the way of the suspension of disbelief.
Oren PeliI don't know. I think that horror, in general, is fairly popular. It's definitely popular in film. There's just not a lot of good horror on TV, so whenever there is good horror on TV, people rush to it.
Oren Peli