The Social Network is probably the best film ever made about the Internet, but that’s not saying much. What’s its competition — The Net? Hackers? Johnny Mnemonic?

Of course, director David Fincher’s semifictionalized origin story of Facebook is about more than the Internet. It’s a bold effort to use a single figure — Mark Zuckerberg, who was a Harvard undergrad when he founded the social-networking behemoth — to encapsulate a historical moment.

Fincher pulled off that trick for the 1970s in the little-seen Zodiac (2007). But that was a low-key film that eschewed the clichés of its genre in favor of something rougher and more real. The Social Network is anchored by something real, too: a career-making performance from Jesse Eisenberg. Whatever you think of his portrayal of Zuckerberg as a mean-spirited, jittery hacker with a status obsession, it’s a landmark. The film’s weakness is the screenplay by Aaron Sorkin, who apparently never met a cliché about the Internet or the Ivy League he didn’t like.

Yes, the “West Wing” creator has a gift for smart dialogue. He shows it in the movie’s opening scene, which is also its best. Over the course of a single conversation, Zuckerberg goes from having a girlfriend (Rooney Mara) to having a bitter ex-girlfriend. Maybe he shouldn’t have insinuated she’s his intellectual inferior “because you go to BU.”

This scene tells us everything we really need to know about Eisenberg’s character. Because he’s insecure, he needles himself and everyone around him, probing for weakness. Driven to dominate one small corner of an overwhelming world, he invents something that starts as a form of revenge against the girl who rejected him and grows into a cool clique he controls. “It’s like a final club,” he tells his friend and business partner, Eduardo Saverin (Andrew Garfield), “except we’re the president.” Since the film’s main narrative is intercut with scenes of an older Zuckerberg battling Saverin and others in lawsuits, we know by the end he’ll have booted them from his inner circle.

This “lonely at the top” stuff isn’t new. But the jockeying for position among Zuckerberg, Saverin and Napster founder Sean Parker (Justin Timberlake) — who finds out about Facebook and angles for his own piece of the pie — makes for an absorbing clash of personalities. The movie would have been far more compelling if Sorkin and Fincher had kept their focus there.

Instead, they spend too much time on Zuckerberg’s other eventual legal antagonists, the smug, preppy Winklevoss twins (both played by Armie Hammer), who never transcend caricatures. The Winklevosses are everything Zuckerberg desperately wants to be, we’re asked to believe, because they row crew and belong to the invitation-only Porcellian Club. Here I have to agree with Nathan Heller, who argued recently in Slate that Sorkin’s view of Harvard is as retro as Love Story. I remember students rolling their eyes over final clubs during the Reagan administration.

But corny elements could be forgiven if the film’s dialogue and plotting weren’t so often heavy handed, too. Rather than letting events speak for themselves, Sorkin uses characters to make his talking points. When Zuckerberg tells lawyer Rashida Jones he’s expanding to Bosnia, she shakes her head and says, “They don’t have roads, but they have Facebook.”

We get the point: A social network isn’t a functioning society. Zuckerberg has 500 million “friends,” but he doesn’t have ... friends. These are strong points, no doubt. But seeing characters used to prove a thesis is never as interesting as seeing them act with the unpredictability of real people.

Here’s a status update: Yes, controlling personalities with Napoleon complexes thrive on the Internet. Too bad this film seems to have been made by as well as about them.