Secrets drive the plots of some of the best movies. Memories are erased, alibis are fashioned, characters are killed or imprisoned and Jedi knights are kept working on farms for far too long, all to keep us guessing, interested and watching. That being said, sometimes a secret is only as good as the writers' ability to cover huge gaps in logic -- gaps that, when you think about it, are so huge that you can drive a bus through them, such as how the hell no one figured out Bruce Wayne was Batman in the Dark Knight trilogy.
#6. The Dark Truth Behind Robert's Magic Trick in The Prestige
Robert Angier (Hugh Jackman) is a magician hell-bent on winning a battle of wits against a rival magician to see who can better perform a specific trick, because this is 19th century England and women would have sex with you for such a thing.
"No syphilis and magic tricks? Deal."
Robert commissions Nikola Tesla to build him what is essentially a teleportation device, with the hopes of using it to dazzle audiences with the greatest magic trick anyone has ever seen (and not, for some reason, to rob all of the banks in the world). The problem is, Tesla's machine makes a copy of whoever uses it, teleporting either the user or the copy in the process and leaving the other standing in the device like a jackass. Robert decides to go ahead and use it for the trick anyway, installing a trap door beneath the machine to drop whichever clone was unlucky enough to be left in the device into a water tank beneath the stage, drowning him like a contemporary orphan (because at this point of the movie, Robert's brain is plucking the screaming bowstrings of insanity). This leaves only one Robert to take a bow after his apparent teleportation across the theater, and only one Robert to cash the subsequent paycheck.
"I'M ALIVE! Uh, I mean ... ta-daaaa!"
To keep the true nature of the trick a secret, Robert only hires blind stagehands and allows no one else backstage, and gets a new water tank for every performance. He has his blind employees cart out his floating dead Robert clones and store them in a warehouse, for reasons that are never adequately explained.
Perhaps because the greatest sin against nature is hiding your sin against nature.
OK, so when Robert books the theater for his Transported Man trick, he specifies that he'll be doing five performances a week for a total of 100 performances. That's 100 tanks over the course of 20 weeks. Where the hell is he getting all of them? There's no way to invoice that many tanks of that size and be subtle about it. And anyone who checks that order and reads a review of his magic show will immediately notice that not a single tank is being used onstage.
And it isn't like Robert is doing the trick once or twice before folding his tent like a gypsy to move to another town. He is performing his show five times a week in the same city for five damned months. He's parading his dark secret around in the open for anyone with half of a brain not poisoned by mercury from a yet-unregulated fishing industry to figure out. That's like hiding treasure in a box labeled "THIS IS NOT WHERE THE TREASURE IS." Moreover, Tesla, the guy who built the machine for him, knows full well how the device actually works and is bound to hear about Robert's famous trick sooner or later. How long do you think it will take Tesla, one of the most famous geniuses in history, to deduce what Robert is up to?
#5. Charles Xavier's Whereabouts in X-Men: First Class
Persecution, racism and the right to anonymity are the underlying themes of the X-Men series. After all, a person's ability to melt buildings with their eye lasers or lift submarines out of the ocean with their mind is nobody's business but their own. This is why Charles Xavier decides to keep his school hidden from the government, because as the climax of X-Men: First Class demonstrates, people tend to overreact to things they don't quite understand.
Calling in Michael Ironside is nearly always an overreaction.
Up to this point in the film, however, both Xavier and Magneto have been working openly with the CIA to help take down a much more devastating threat to the world. In fact, they put together an entire team of mutants to help, and manage to work together fairly effectively until the government turns on them and tries to melt them into radioactive goo (see Michael Ironside, above).
As a result, Magneto vows to murder humanity and Xavier gets paralyzed and goes into hiding. His final scene takes place at his countryside battle mansion/training school, where he and CIA agent Moira MacTaggert discuss the fact that obscurity is the key to the X-Men's success.
While Moira insists that she would never reveal his whereabouts to the CIA, Xavier decides to make doubly sure by erasing the knowledge from her head with a memory-boiling mind laser.
If he can do that, why can't he use his superbrain to make his fucking legs work?
But how exactly is erasing Moira's memory going to keep the CIA off of Xavier's back? After all, he's been working for them for months, using his real name. They know everything about him -- his family, his field, where he went to school and the location of his mansion.
The final scene in the movie shows Moira's CIA superiors exasperated and seemingly helpless at her loss of memory ... but how could this be? Could their frustration really last any longer than a few minutes of grumbling and a demotion? After all -- they know exactly who Charles Xavier is. He's the wealthy, prominent mutant who worked for them for months under absolutely no disguise. We cannot stress that enough. He probably filled out a freaking W-2.
"If only we had some way to locate him using only his name and address ..."
#4. Peter Parker Keeping His Secret Identity from Friends and Family in Spider-Man and Spider-Man 2
All superheroes want to keep their identity a secret (unless they're one of the Avengers, in which case it doesn't seem to matter). Spider-Man is no different. He wants to keep his life as Peter Parker separate to spare vengeful, inciting attacks on his friends and family.
Peter turns Mary Jane down at the end of the first film because he knows that to be with her would expose her to his self-spun web of constant mortal danger.
And not because she tried to make out with him in a goddamned graveyard.
Peter continues to deflect her throughout the second film, even as she parades a wedding to some spacedouche in front of his face, until he finally just tells her that he's really Spider-Man. Even with that out of the way, he still fights her, saying, "If my enemies found out about you ... if you got hurt, I could never forgive myself."
It sucks, but it makes sense, right?
Actually no, it makes the complete opposite of sense. You see, while Parker doesn't publicly reveal himself as Spider-Man, he does admit to being Spider-Man's friend and "personal photographer," a title that covers exactly as much ground as you care to allow it.
"No one will guess I'm secretly a stupid kid."
We now ask you this -- what, to a hostage-taking supervillain, is the difference between being a superhero and being a superhero's friend? If you don't want your friends to be in danger because you are Spider-Man, it's not really a great plan to go around announcing that Spider-Man is a friend of yours. That's actually worse than just coming out as Spider-Man, because if everyone knew you were Spider-Man, no one would dare fuck with you or anyone in your general vicinity without expecting a full-on superpowered melee. However, if the bad guys think you're just another ransom note in the making, you are spreading a big fat target over yourself and everyone you care about.
"Mary Jane! I swear this is the last climactic battle you'll be involved in!"
Peter Parker's friends and family get attacked in both movies for this explicit reason. Remember when Dr. Octopus hurls that car at Peter and Mary Jane while Peter is busy stutter-mumbling his way out of guaranteed sex? Doc Ock isn't doing that because he knows that Peter is Spider-Man -- he's doing it because he knows that Peter is friends with Spider-Man. Keeping his identity secret doesn't help anyone if he singles out himself, Peter Parker, as a viable target. In fact, in that case it would be better if he told Mary Jane and Aunt May he was Spider-Man so they wouldn't be totally confused by all the maniacs that ambush them.