What I like about things like Marble Hornets though, is that they present themselves as a sort of real-time documentary. Like it's actually happening, and this person wants to bring the world on their messed up crazy ride - and let people know what's going on if anything happens to them. Like you're along for the adventure.
With a movie - even if it's presented like Cloverfield or The Blair Witch Project, it won't have the same feel as watching something presented as an ARG.