Horror films are reliant on having sad plots. If there's not a death or a past trauma then there isn't a lot to build something scary off of, is there? But most horror film tread the line of bleak plots and new beginnings (ie a family moves in to a haunted house, the ghost that haunts those woods dies years ago) which gives the characters distance from the trauma, they are removed from it.
In films, particularly exploitation films of the 70s and some more recent found footage horror films deal with a present trauma. Something that is occurring for the first time in the world of the film. These horror films are what I like to call B.A.F. (Bleak As Fuck) they are so morose and sad that they are a chore to get through in many cases. Most recently some of us may have seen Megan Is Missing (2011) a found footage thriller/horror about the dangers of online chat rooms. (BJ-C over at Day of the Woman has a great write up about it here) This film is a slog to get through. It repeatedly reminds us of the dangers in our own lives. It's goal is to seem familiar and particular to us and our worldview which is part of the problem.
I am a huge believer of the spoonful-of-sugar method. If you can entertain your audience then you will have access to a bigger portion of them. The plot of Megan is Missing and something like The Poughkeepsie Tapes are too on the nose. If we are to believe there's a serial killer in every town and every person on the internet wants to kidnap us it makes for a rather bleak world view. Moreover is sensationalizes the trauma of actual cases like these. Since the filmmakers for the movies have said that these films (Megan is Missing and The Poughkeepsie Tapes) are a composite of real cases it brings a rational fear to a largely irrational medium.
Straight up, I don't like these films. They drag, they are borderline snuff films and frankly fail at delivering some kind of larger world view or moral implication. If we look at other sad horror films they are framed like fairy tales, their world is a complete and complicated world. By watching a film like Carrie or The Fly or The Shining we gain a larger understanding of humanity. In The Poughkeepsie Tapes the film is intercut with videos a serial killer made and left for police and interviews with the police that tried to catch him it is specific and obsessive. There is nothing but perverse titillation.
I think the core problem with these films is that the victims remain victims (you could easily say the same thing about characters in a Saw or Hostel movie). They do not exist in the larger world, we have little to no context about them. Films work when they teach us something about the larger world. The Shining teaches us about family and intimacy, Carrie teaches us about becoming a woman and repression and The Fly teaches us about romantic relationships. They are thrilling visceral movies but they also work allegorically. Megan is Missing and The Poughkeepsie Tapes work only to disturb and frighten. They have so little context and understanding of the world that to me they seem eerily close to snuff films.
I had a conversation last night about this very topic. The other person said, well wouldn't something like Martyrs fit into that context? I think something like Martyrs or Inside comes very close to that but it is our identification with the victims, their perpetrators and their very human struggles that elevates them to a personal and intimate level which in my mind makes them even more terrifying. Something like High Tension would fit in with my critique of Megan is Missing and The Poughkeepsie Tapes because there is no rhyme or reason.We understand so little of the victims and so little of the aggressors. All we are left with is that people are evil. However, simply being "evil" or "sick" isn't the answer. It's an excuse to shock. But when the shocks become boring and forgettable then we as an audience have learned little else except, don't talk to strangers. I would say it's a greater challenge and accomplishment to examine the hows and whys of acts like this, not merely shock us with disturbing images.