Continuity mistake: At Hagrid's hut, when he places the dragon egg on the table, the book lies right next to the cup and saucer. Yet in the shots looking up from the edge of the table, directly in front of Hagrid and the egg/Norbert, the book and cup/saucer are far apart for these particular shots. (01:39:50)
Continuity mistake: When trying to catch Neville's Remembrall, Harry flies straight for McGonagall's window. The window visible in the wide shot has a horizontal beam that crosses the center vertical beam, yet the window visible in the close-up just has the vertical beam. The number of stones at the sides differ as well. (00:58:30)
Continuity mistake: While Harry and Hagrid stand beside Hogwarts Express, in the shot looking up at Hagrid as he takes the album out of his pocket, his thumb is on the back cover as he begins to say, "This is for you," yet in the next shot of Harry taking the album, Hagrid's thumb is on the front cover. (02:22:05)
Continuity mistake: On the Hogwarts Express, Hermione first watches as Ron tries to turn Scabbers yellow, she then joins them inside before she actually leaves and in these consecutive shots, her tie differs. (00:36:30)
Continuity mistake: Mr. Ollivander says, "I wondered when I'd be seeing you Mr. Potter," and as he climbs down the ladder Harry is standing at the middle of the desk, away from the corner. In the next shot as Mr. Ollivander searches for a wand case Harry stands at the corner of the desk. However, in the next shot Harry stands at the middle again. (00:25:30)
Revealing mistake: At the end of the film, when Harry is leaving on the Hogwarts Express, and the overhead shot shows the train pulling away from the station you can clearly see that Hagrid is of normal height, as the train roof is much taller than he is. (02:23:40)
Continuity mistake: The shape of Harry's scar changes dramatically in quite a few shots throughout the film. Two examples being, the morning of Dudley's birthday, when Harry opens his eyes in the close-up, while lying in the cupboard and later, when his hair is blown back in the close-up as Voldemort's 'spirit' starts to rush through him while he holds the Stone. (00:04:05 - 02:13:25)
Continuity mistake: In the scene where Harry, Ron, and Hermione are walking towards Hagrid after their exams, Hermione is carrying a brown satchel in her right hand. Then Harry says, "Why didn't I see it before!" and they run. While they are running she does not have the satchel in either hand, her empty left hand is visible in a few frames as she swings her hands at the side of her body. Then when they get to Hagrid she has the satchel in her left hand. (01:46:40)
Continuity mistake: In the sea hut scene, when Dudley steals the cake, there's a shot of him eating it and his pyjama shirt is pulled up, then it cuts to Hagrid, and he says 'He'll be under the finest headmaster...' and it cuts back to Dudley, but his pyjama shirt is back down over his pyjama pants. (00:17:10)
Continuity mistake: When Dudley is told how many presents he has, and he asks, "How many are there?" a cut to him shows that his fringe is a bit untidy. Scene cuts to his Dad. When it cuts back to Dudley, his fringe is much neater. (00:05:04)
Revealing mistake: When the letters burst through the letter opening that has been covered by a piece of wood, you can see that the piece of wood was pre cut. (00:12:00)
Other mistake: In the scene where Professor Quirrell removes his headwrap to reveal the concealed Voldemort, Quirrell is obviously bald. However, if you carefully watch the scene with the troll, Quirell's sideburns are present after he shudders as the troll exhales, as they are in a couple of other shots. (01:10:43)
Continuity mistake: In the scene straight after the Quidditch match where Harry, Hermione and Ron are telling Hagrid about their suspicions of Snape, you will see all three are wearing scarves tied in different ways. When there's a change of shots, the creases in the scarves change. This happens mostly with Hermione's. (01:23:55)
Revealing mistake: When Harry and Hagrid are at Gringotts and are pulling up in the cart to Harry's vault, in the overhead shot you can see the various levels bellow them. In the next shot in the lower left corner you can see what appears to be blue screen just bellow the walking surface. (00:22:10)
Continuity mistake: When Hagrid and Harry step out the back door of the Leaky Cauldron, in the overhead shot there are many glass bottles on the floor, between the barrels. However, after Hagrid says, "Welcome Harry, to Diagon Alley," as they walk out the barrels are visible behind Hagrid and there are no glass bottles between the barrels. The stone ground differs in both shots too. (00:20:05)
Continuity mistake: As the students board the Hogwarts Express to go home, the cuts on Harry's face, particularly near his eye, differ during this scene depending on the camera angle in a given shot. (02:21:55)
Continuity mistake: In the scene where Harry and the Dursleys visit the zoo, the first shot you see of the snake, he is lying on a bare rock with only moss on it. He is also lying with his head facing the window, and his body is curving to the right. However, after Dudley walks away and the shot returns to the snake, his body is curving to the left and now there are plants directly behind him where there was only moss before. (00:06:00)
Continuity mistake: While the first years are waiting at the top of the stairs just before being lead into the Great Hall for the first time, Ron's robes switch from being fully opened, to closed, then back again. (00:40:00)
Continuity mistake: When Hermione is saying to Harry and Ron "You won't make a fool of yourself, it's in your blood," Harry and Ron have several books with them, but straight after, right before the staircase moves, they have no books in their hands. (01:00:35)
Continuity mistake: At Platform 9 3/4, when Mrs. Weasley says, "All right, Percy, you first," as Percy walks in front of her she holds her bags in her left hand. Yet in the next shot as Percy still walks in front of her, she holds her bags in her right hand. (00:32:25)
Chosen answer: There are several reasons. First, the position is cursed, so there is little reason to give Snape the job when he will not last any longer than all the previous instructors. If Snape did become the DADA instructor, something could happen to him that could result in his being harmed, having to leave Hogwarts, or be otherwise incapacitated in some way; that would render him useless to Dumbledore as a double agent. Also, Dumbledore trusts Snape, but putting him in an environment where he is teaching about dark magic on a daily basis would be too tempting and emotionally compromising to someone who had been so easily seduced by the dark side. He could possibly relapse. It would be like having a recovering alcoholic work as a bartender. Of course, he does eventually become the DADA instructor, and lasted no longer than his predecessors.
raywest
In the movies it is never mentioned that DADA role was cursed by Voldemort.