Continuity mistake: When Peter looks at Gwen's mementos, the photo he had in hand and the USB key both change position between shots. (02:07:50)
Continuity mistake: Peter is absent-mindedly listening to the news while Aunt May is putting away some objects. There's a cut while the speaker says "return of the web-slinger" and May who just had put down some letters is suddenly lifting a book. (02:06:25)
Continuity mistake: The one kid Spidey helped is looking at the window during the news story about Rhino breaking out of prison. He leans forward, but he's in a different position between shots, and his wind turbine is powered up only in the last shot even if it was still two shots before. (02:06:15)
Revealing mistake: As he holds the dead Gwen in his arms, Peter says "Stay with me, stay with me" two times, twice, and then a fifth time "You stay with me." Between the two repetitions, you can see Emma Stone's long eyelashes twitch. (02:02:30)
Continuity mistake: In the final battle, Spidey is going hand-to-hand with Goblin while Gwen is still dangling. At one point he wraps his web around Goblin's neck; the two loops of web change distance depending on the camera angle. (02:00:10)
Continuity mistake: When the sickly kid CEO overpowers the two security guards, he does so with the one on the right that mysteriously in one shot is facing him and in the next he's facing the nearby desk, away from him. (01:33:35)
Audio problem: When Harry listens to the recording of Electro's threats to Dr. Ashley Kafka, the sentence is conveniently edited for brevity, omitting part of the original sentence ("A world without mercy"). (01:15:25 - 01:28:40)
Revealing mistake: Harry Osborn types "Special Projects" (and we see the word taking shape as he types) hitting as the last keys "E", space bar and "G." (01:28:05)
Continuity mistake: When Peter for some reason decides to try to hoodwink the English receptionist pretending to be "John Hopkins", he mentions that he tried to get Gwen to be part of "my team." In that, a guy comes in frame walking from right to left. Several seconds later, same extra, same walk. (01:24:20)
Continuity mistake: During Peter's rant inside the Oxford office, Emma Stone's hair comes and goes from the front of her right shoulder. This happens all the way throughout the scene, even at the pivotal moment at the very end when she asks him which was the "one thing" he mentioned. (01:23:20)
Continuity mistake: Inside Oxford's North American office, Peter starts blathering; he says "Everything's a mess", he says; Emma Stone in the next shot has her hand raised. The mistake happens again at the end of the conversation when Peter goes "I'm sorry to bother you", and her raised hands go down her sides from the wide shot. (01:23:15)
Continuity mistake: When Harry is talking to Spidey that barely camouflages his voice, the hair on his forehead keeps changing position between shots. (01:21:20)
Continuity mistake: Peter inputs in Google "What is Roosevelt?" and gets as output for his search "Franklyn Roosevelt + New York" (01:01:25)
Continuity mistake: Harry wakes up to Spiderman's voice in his living room. He sits and looks at him. Notice the messy hair on his forehead. Changes shot (he is rubbing his nose like Gwen, just not as cute) and his hair is combed over properly. (01:20:50)
Continuity mistake: Peter comes back home and finds his aunt sitting on his bed staring at his serial killer-like collage. The two start talking, and during the conversation May has several locks of hair on or off the cheek as the two angles alternate. (01:16:45)
Continuity mistake: During the kiss in closet scene, Garfield has his hand on Emma Stone's face abruptly at the cut. Seconds later, when they concur that the kiss was "a bit rushed" they smile at each other with a completely different position - as you can see from the light rays on their faces. (01:10:55)
Continuity mistake: Peter is cooped up in the garage window as he answers the phone after a night of dangerous experiments. First shot and his arms are free, close-up, and he's wrapped in a blanket. (01:05:00)
Continuity mistake: Harry just found by accident the secret interactive desktop from his father. He drags and drops a menu, but somehow when he checks out the item he highlighted, the menus themselves changed entirely showing stuff like "Max Dillon experiment" that were not there a moment before. (01:03:05)
Other mistake: We see Peter freshly printing an old news story from CNN; the timestamp on the visible corner says the sheet was printed at 9:18 AM. The scene takes place in the evening. (01:01:45)
Continuity mistake: Watching the news after his confrontation with Electro, Spiderman picks up from the table the webbing device that got fried. He then throws it back on the table, where meanwhile all the tools shifted around randomly. (01:00:40)
Answer: Peter could have contacted the police anonymously.
MasterOfAll