Found footage movies have their precedents in literature. A number of HP Lovecraft's classic stories were written in this way, often starting with 'text found in a bottle off the coast of Norway' or 'audio recordings recovered from last known base of Exploration Team 415Alpha'. And this was in the 1920's and 30's. I seem to recall Edgar Allan Poe writing at least one as well. I wonder how much further back 'found stories' go?
How about "Letters of a Portuguese Nun" from 1669? (Sort of remade by Jess Franco as a nunsploitation porno).
The earliest novels were often/usually printed as a collection of "found" letters or documents. ("Dracula"--1897--is another example).
Good posts, both of you. I don't see an inherent problem with the sub-genre. It's all in the execution, always. They are a challenge to execute well, however. At least for me. The challenge comes in justifying the camera rolling as much as it does. This is difficult to do, and so most of them tend to fail.