Deliberate mistake: When Spidey jumps on the hood of the truck, Rhino squirts him using the wipers. Funny, but he can do that only because the detergent sprays forward instead of the angle actual windscreen washers are pointed at. (00:12:50)
Continuity mistake: When Gwen is giving her speech, in the background are two boats passing. In the next shot they disappear. (00:12:50)
Continuity mistake: After saving a bus, when Spidey confronts Rhino the big puddle beside him disappears between shots. (00:13:45)
Continuity mistake: While Rhino is getting webbed by Spidey on the street, the sun changes between shots. (00:13:55)
Continuity mistake: When Stan Lee is in the audience of the school ceremony, in the close up somebody is on his left but in the open view that person is gone. (00:14:20)
Continuity mistake: When Peter is kissing Gwen by the podium, Garfield's right hand is on Emma Stone's cheek, but in the reverse angle his hand is on the middle of her back. (00:14:35)
Continuity mistake: When Peter greets Aunt May during graduation a bang of hair over her left cheek appears/disappears randomly between shots. (00:15:00)
Continuity mistake: During graduation, after Peter tell his aunt "Ralph Waldo Emerson" he takes his hand to his hair. A shot later the hand is lowered. (00:15:15)
Continuity mistake: In the scene where after Peter gets his diploma and has a chat with Gwen, he is carrying a backpack on both shoulders. As the scene continues it switches to one shoulder then both several times. (00:15:50)
Continuity mistake: When Aunt May takes a picture of Gwen and Peter she places two left fingers on the camera. When the angle changes there's just one. (00:15:50)
Continuity mistake: After Aunt May takes a picture of Gwen and Peter they're standing side by side. A shot later they're a meter and a half away from each other. (00:15:55)
Continuity mistake: After graduation, when Peter kisses Gwen he places his hand on her cheek. When the shot changes the hand is gone. Also, her hair is covering her cheek or perfectly brushed depending on the angle. (00:16:25)
Continuity mistake: When Gwen is summoned by her parents to take a graduation family picture she says to Peter she'll work "all night long" and places her left hand on Peter's neck. When the shot changes her hand is gone. (00:16:30)
Continuity mistake: Coming out of the Chinese restaurant, Emma Stone is closing her coat, and you can see in the view from behind that she even completes the movements to properly tie the belt. The scene continues, the belt is perfectly fitting and closed, but the last shot of the scene shows Gwen Stacy in front of the door with the coat open and the belt loose. (00:17:35)
Continuity mistake: The little bullies are pushing the wind turbine kid against the fence; they literally have their fingers inside the links; they look up and notice Spidey, barely move very slowly, but a moment later they are much further back in the alley giving him a solid few meters of space where he lands. (00:20:35)
Continuity mistake: When the Statue of Liberty tells Spidey "Nice outfit!" the people in the background are in different positions at the cut. (00:21:20)
Continuity mistake: When Peter pulls the boot of the costume under the cover to prevent May from seeing it, you can get a good look at the stack of books he's going to trip into a few seconds later. In fact, you can still see even as he trips, that the stack includes the famous leather bag from his father. He doesn't knock it to the floor when he trips, but the next shot just shows it on the floor anyway. (00:23:25)
Revealing mistake: Max is having a delusional monologue at the mirror with his imaginary friend. You can notice that the 'gap' between his teeth is represented by a piece of black tape. (00:24:30)
Continuity mistake: When Aunt May is about to do the laundry she gives Peter a sandwich with a large piece of lettuce in it, but in the following shots the lettuce disappears. (00:26:40)
Continuity mistake: When Max is talking to his boss and fantasizes to assault him, there's a woman walking past them reading some documents, and she keeps coming from the corridor and passing them by - that's without considering Max's fantasy, just shots of the 'real' events. (00:27:50)
Answer: Peter could have contacted the police anonymously.
MasterOfAll