When a formula works, the film industry is notorious for stubbornly stamping its foot down on the gas and staying firmly in that lane until the wheels fall off. Ever since 1999's The Blair Witch Project turned an estimated $60,000 budget into more than $240 million in worldwide sales, using the "found footage" conceit pioneered in 1980's Cannibal Holocaust, the shaky, handheld style has been a constant in horror movies, and even other genres.

Clever filmmakers have come up with rock-solid explanations for why the footage in their movies exists. Jaume Balagueró and Paco Plaza's 2007 Spanish surprise [REC] unfolds through the camera of a documentary news crew as it captures a viral outbreak turning quarantined apartment residents into bloodthirsty savages. In Oren Peli's Paranormal Activity (2007), a haunted couple sets up cameras around their home to record evidence of the disturbing presence. That setup worked so well that PA, made for an estimated $15K(!!!), raked in over $180 million and spawned two equally successful sequels. This week, Ariel Schulman and Henry Joost's entertaining (though not mythology-expanding) Paranormal Activity 4 introduces teenagers' video chats to the series seamlessly.

For every intelligent director-producer team concerned with details, there are several lazy imitators who force the concept of found footage into their flicks when it makes absolutely no sense for the characters to be filming. In the hope that genre films try a bit harder, Complex scrutinizes The 7 Worst Justifications for Found Footage in Movies.

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Written by Frazier Tharpe (@The_SummerMan)