Alternative Character Interpretation: Heather seems to be filming almost constantly the whole time they're in the woods, long after almost anyone would've stopped. Her motivation for obsessively documenting everything becomes less and less clear, and throughout the film she gets a lot of footage she couldn't reasonably expect to use even if they did manage to get out of the woods, such as her and Josh violently berating and briefly physically attacking Mike for destroying the map, and multiple instances of herself sobbing, during which she makes sure the camera is pointed at her. Mike even has to stop her from recording Josh's breakdown, and throughout the film a major source of conflict among the group is the fact that Heather just won't turn the camera off.
Toward the end of the film, Josh suggests that the reason Heather is "still making her movie" is because it allows her to disassociate from the reality of the situation; the danger and hopelessness are less real if she's only watching them through a camera lens as a movie, not something she's a part of.
Complete Monster: From the Alternate Continuity tie-in prequels, which have a Shared Universe with Nocturne, Hecaitomix is the evil spirit behind Elly Kedward and Rustin Parr, starting the Blair Witch legend, and the true source of the curse. Angered that he is no longer worshipped, Hecaitomix spent centuries torturing and killing, children specifically, with the goal of wiping out the human race and ruling over what's left. Hecaitomix disemboweled a child, dubbed the "bleeding child", and kept him alive to feed on before trapping the child in his realm. He also conquered a spiritual realm and turns the spirits there into demons. Hecaitomix has Robin Weaver abducted and attempts to possess her, and in the ritual traps children's souls and keeps mutilated victims alive and conscious. He bargains with a man to cure his blindness and turns him into another demon to do so. After Rustin Parr's killing spree, Hecaitomix possesses Kyle Brody to use him as a new vessel, before moving on to a local pastor and plots to abduct Mary Brown to subject her to the same fate as he did the bleeding child.
Epileptic Trees: Fans have gone on for pages and pages debating what is attacking the main characters in the movie.
In spite of good reviews and having its fans, some didn't like the movie upon its release. In fact, the first film was nominated for Worst Picture by the Golden Raspberry Awards and Heather Donahue even won for Worst Actress.
While 'found footage' movies suffer this in general nowadays, at the time almost everybody agreed the technique was unique. What divided most audiences was the ending: it either blew you away and left you paranoid/scared of being alone for a few hours or days, left you amused and curious, or left you furious and wanting your money back.
There is some argument that audiences who love the movie and audiences who hate the movie are split by those who live in suburban or rural areas and could relate more towards local urban legends, people disappearing, scary woods, and those who live in the city and wouldn't have any association with those things.
It goes way beyond that. Some people hate the movie because they just don't believe in the supernatural at all, so consider the very premise ludicrous. Others hate it because they believe wholly in the supernatural, and complain the kids were totally ill-prepared for walking into haunted woods hunting a possible Eldritch Abomination, making the kids Too Dumb to Live. Others hate it just because they think it should have a motion sickness warning in the opening. People who love the movie love its tense atmosphere, innovative (at the time) storytelling device, and the pure, distilled Nothing Is Scarier approach. But almost invariably, people either think this is one of the best horror movies ever made, or a complete waste of time.
Narm: Heather's apology is a chilling scene, but the booger hanging off of her nose has taken more than a few people out of it. Scary Movie parodied it by having a geyser of snot pouring out of Cheri Oteri's nose during its take on the scene.
Nightmare Retardant: If the film scared you, watch it with the DVD commentary and that'll quickly change. The producers all goof around discussing things like getting the rights for the groceries in the movie, Josh being "abducted" so early because he had to go to work on the third day of filming in the woods, and how the actors tried to jokingly catch them on camera when making noise in the middle of the night. The creepy image of the children's hand-prints on the halls of the old house is a bit hard to take seriously when the producers talk happily about bringing a gaggle of kids in in and just how much fun they had smearing their handprints all over the walls.
Paranoia Fuel: Try going to the woods after watching this movie and not feeling like something's watching you...
Rewatch Bonus: A lot if you check out the tie-in materials and backstory. If you know a certain aspect of the Rustin Parr story, (that he marked the graves of the people he killed with piles of stones), then you'll discover that the characters were doomed from the start.
Seinfeld Is Unfunny: In these days of dime-a-dozen "found footage" horror movies, it can be pretty hard to remember just how innovative the gimmick was in 1999.
Signature Scene: The apology scene, quoted atop the work page, in which the camera focuses on half of Heather's face as she stammers through an apology, alone and scared out of her mind.