Continuity mistake: When Dumbledore brings Harry to meet Slughorn, the Daily Prophet is lying on the floor amongst debris, including the piano's hammer, which differs between shots. (00:06:50)
Continuity mistake: In Potions class, when the students prepare the Draught of Living Death, as Harry tells Hermione, "Crush it, don't cut it," the way he holds/squeezes the Sopophorous Bean has instantly changed from the previous shot.
Continuity mistake: At the Burrow, when Tonks and Lupin are at the front door with Mr. and Mrs. Weasley, it cuts to an exterior shot of Harry looking out the window with his arm leaning across his knee in front of him, but in the next interior shot his arm is down at his side.
Continuity mistake: At Slughorn's party, Harry and Slughorn have their picture taken. Before and after the flash the background changes completely without enough time to change.
Continuity mistake: When Dumbledore is talking to Harry about Horcruxes, Dumbledore's hair is blowing and messy in one shot, but fine in the next shot.
Continuity mistake: At the diner when Harry walks toward the windows, in the close-up of a window through which we see the distant platform (before Dumbledore appears), the style of the window's muntins (sash) around the glass panels is quite different in this close-up, than in the previous shots of the windows. (00:04:00)
Continuity mistake: On top of the Astronomy Tower, before Dumbledore and Harry leave to retrieve the locket, Dumbledore hair moves in front of his left shoulder in shots behind him. (01:57:35)
Continuity mistake: In the Great Hall, when Lavender's eyes are shooting daggers at Ron and Hermione, Harry's arms/hands keep changing position on the table as the three of them speak.
Continuity mistake: At Aragog's funeral, there is a long shot of Slughorn, Hagrid and Harry standing by Aragog. However from this angle Aragog is not here. Given the angle you should be able to see Aragog's body.
Continuity mistake: At the Three Broomsticks, Slughorn is holding a mug with his left hand when he speaks to Harry, but when he says, "Good to see you, Wallenby," the mug is suddenly in Slughorn's right hand, with his left arm down by his side. (00:51:15)
Continuity mistake: In Potions class, when Slughorn removes the vial of Felix Felicis, he turns to face the class and holds the vial up for the class to see, but in the next shot facing him he holds only the very bottom point of the vial. (00:35:15)
Continuity mistake: When the Death Eaters attack Ollivander's, the debris/fire and the bodies lying on the ground differ between the overhead and next close-up.
Continuity mistake: At the Burrow, when Ron takes a seat between Ginny and Harry he is holding a pedestal plate full of pies, which change in the next shot facing the other way.
Continuity mistake: In Hagrid's hut, when Slughorn and Hagrid are drinking, the cups/bottle on the table change position between shots.
Continuity mistake: Aboard the Hogwarts Express, when Draco petrifies Harry he falls immobilized. Just as Draco kicks him, Harry's head is positioned farther out in the aisle, than previous and following shots. (00:26:40)
Continuity mistake: When Luna and Harry pass through Hogwarts gate, the parchment and wand in Flitwick's hands differs between shots.
Continuity mistake: When Ron is foaming at the mouth, the foam is either there or it's not, depending on the shot.
Continuity mistake: At the Muggle orphanage, in the corridor when Mrs. Cole says, "Tom, you have a visitor," Dumbledore's scarf hangs askew, but next shot facing him the scarf hangs properly. (00:40:05)
Continuity mistake: The glass that is smashed in the Great Hall's window behind the staff tables changes somewhat from when Bellatrix smashes it, and when we are shown the Great Hall empty.
Continuity mistake: When Dumbledore and Harry are talking about Horcruxes, Harry's hair is nice and combed in one shot. The camera cuts to a side view and his hair is now messy.
Answer: Leaving an untrained young wizard, who obviously has some behavioral issues and has no idea he is magical, alone in the Muggle world would be extremely dangerous. Dumbledore does not yet know that Riddle will become evil, but like any teacher, he wants to give a troubled youth an opportunity to find a new path in life.
raywest ★