Revealing mistake: There is a shot of the Fellowship in Moria running towards camera as the entrance collapses behind them, in this shot you can see that the hobbits are obviously not Elijah, Sean etc. but their scale doubles. (00:18:15)
Revealing mistake: After Boromir is shot twice, he turns around and kills one Uruk Hai, and then when he kills the second one, you can see the sword wiggle after he slices the enemy's legs.
Revealing mistake: At Rivendell when Frodo puts the Ring on the stone table in the middle and then Gimili says his, "I'd rather die than see the Ring in the hands of an Elf" Gandalf stands up an makes a sort of "you're out- like an umpire" move at someone while they are all arguing, when the camera is on the people. When they go to the reflection on the Ring, Gandalf makes the movement again. Clearly it is the same shot again.
Revealing mistake: After Bilbo returns from the party invisible and finds Gandalf by the fireplace, look at Gandalf as Bilbo walks between him and the fire. There is no shadow cast on him when there clearly should be. Also as the camera pans round following Bilbo's movements, you can see Gandalf is casting a shadow on the floor but not on the table, but when Bilbo walks up to it he does, even though Gandalf is between him and the fire light. (00:25:10)
Revealing mistake: When the Fellowship is trying to get to the bridge of Khazad-Dum and are delayed by the gap in the staircase, in one shot, Legolas jumps, in the next shot, Gandalf jumps. Sam is visible for a second, in the upper right corner of the screen, and he is obviously the Sean Astin's scale double wearing a mask. (00:36:10)
Revealing mistake: When Gandalf first sends the Hobbits on their journey, they are in the forest and the Hobbits walk up to Gandalf and the horse, you can tell that the Hobbits are dressed up little people rather than the actors themselves. You can tell by their stature, and how they walk. (00:43:05)
Revealing mistake: In the Prologue, in the shot where Elendil is thrown aside by Sauron and hits a rock and then falls to the ground, you can see his shoulder armor bend, which metal armor should not do. This is because the filmmakers used rubber armor for fighting scenes. This is confirmed on the DVD audio commentary.
Revealing mistake: When Gandalf tells Frodo to 'keep it secret, keep it safe' there is a close-up of Gandalf's face and he is wearing contact lenses. (00:31:45)
Revealing mistake: When Frodo and Gandalf are on the wagon talking about Bilbo, and we see footage of Bilbo in Bag End, look closely at his foot. You can obviously see it bounce, showing that it is not his real foot but a prosthetic one. Extended DVD. (00:12:25)
Revealing mistake: When Boromir cuts his finger with Elendil's sword, the cut appears before he actually touches the tip of the sword which causes the cut. (01:30:30)
Revealing mistake: In Balin's Tomb, after Merry and Pippin are separated from Frodo when the cave Troll smashes its club on the floor beneath them, the Troll first sniffs around the pillar to Frodo's right (viewer's left) as we see Pippin and Merry standing up, before the Troll comes around to Frodo's right and sniffs again. At the start of the next shot, we actually see Merry and Pippin in full view of their facial expressions, standing at the ready, with their daggers held high, continuing to just stare past the pillar behind Frodo. So, despite the fact that the huge Troll is appearing directly in front of them, to Frodo's right once again (before it roars), Merry and Pippin don't even glance in its direction. (00:31:35)
Answer: The temptation of the Ring is directly proportional to the power and ambition of the bearer. To someone like Gandalf - a mighty wizard who wants to save the world - the temptation would, over time, prove to be too much, and he's realistic enough to understand that about himself. With an ordinary hobbit who only wants a nice meal and some peace and quiet, the Ring has a lot less to work with.