This office bulletin board has more on it than coupons and family photos…it also has the key to the mystery of the whole movie.
After Verbal leaves the office, David Kujan sits around feeling momentarily satisfied—he thinks Dean Keaton was the main bad guy, since he just forced Verbal to admit this.
But as he stares at the bulletin board he realizes that something's wrong. Details Verbal has told him were all pulled from the board—from the name Redfoot, to the bit about picking coffee beans in Guatemala, to the story about how Verbal was once in a barbershop quartet in Skokie, Illinois.
When he drops his coffee cup in a gut-sinking astonishment, we see from the broken pieces, that Verbal invented the name "Kobayashi" from the brand of the cup, too.
Kujan's too late to catch Verbal, who shakes off his fake limp and damaged hand, and jumps in a car with a guy who looks like the Kobayashi from the story. Meanwhile, a sketch of Keyser Söze, based on Arkosh Kovash's description, arrives at the station via fax…and it looks a lot like Verbal.
We also see interspersed clips of Söze—who looks like Verbal—shooting Keaton and the other three criminals on the docks. So, Kujan's left behind to learn the bitter truth that super-criminals really do exist, while Verbal hightails it back to whatever secret lair he's going to inhabit now…
When asked about the movie's ending, the screenwriter Christopher McQuarrie refused to explain what really happened in any detail:
The film would not work if it answered all of your questions. I have heard many theories about what happened and some of them are so good I wish I had written them. To me, a film that answers all of your questions is pointless. People are paying a lot of money to support your bulls***. If you don't give them something to take with them, you are a thief, a lousy storyteller. To that end, you also have to take something away from them, rob them of some fulfillment. Without mystery there is no love affair. (Source)
Despite McQuarrie's evasions, it seems pretty clear that we're supposed to believe that Verbal is Keyser Söze. The faxed sketch of Söze looks just like him, he fabricated his whole story, he doesn't really have a limp…what else could be the case?
To make sure you get the point, when Verbal/Söze finally drives off with his chauffeur, we hear a clip of Verbal saying something he told Kujan earlier about Söze,
"After that...my guess is you'll never hear from him again."
The clip wouldn't be playing when Verbal left if we weren't supposed to think that he was Söze…and that Kujan won't ever see him again. That's clearly what most people get out of the movie.
But there are still open questions—like, how much of this story did Verbal really make up? Did Verbal just make up the name "Kobayashi" while describing a real person or invent the whole character? How long was he going by the name "Verbal Kint"? Did he really shoot his whole family in order to show Hungarian gangsters he couldn't be intimidated?
Well, the truth is…we don't know. The movie solves one mystery—the identity of Keyser Söze—while leaving a thousand other mysteries wide open.