Funny thing about the documentary Catfish: I can’t tell you much about what happens in it, but I can tell you plenty about what’s happened because of it.

I can tell you its marketing as a vérité horror thriller (with commercials airing during the MTV Video Music Awards) is the most misleading campaign I’ve seen. I can tell you many folks on the Internet swear Catfish is not a documentary at all, but a nasty hoax whose subject just happens to be ... another hoax.

I can tell you that the debate started when a viewer at Catfish’s packed Sundance screening got up and asked young directors Henry Joost and Ariel Schulman how they could claim the film was real. I can tell you Catfish has become a flash point for independent filmmakers who are pissed off because sweet distribution deals go more often to gimmicky documentaries or faux docs than to dramas.

I can tell you that plenty of critics, including Roger Ebert, maintain their faith that the movie’s events happened pretty much as shown. I can tell you that accusations have flown on blogs, and that the dreaded word “hipster” has been invoked to describe the filmmakers and the documentary’s puppyish, photogenic star, Yaniv “Nev” Schulman's (Ariel’s brother). I can tell you that Joaquin Phoenix probably wishes he could have caused this much controversy and consternation with his own confessed hoax, I’m Still Here.

This tempest in a virtual teacup swirls around a story that is compelling and thought provoking enough to be worth your while. But, to be honest, nothing in Catfish is mindbending enough to induce all this disbelief.

Here’s the setup: Nev Schulman, a 24-year-old New York photographer specializing in ethereal images of dancers, gets a MySpace message from an 8-year-old Michigan girl who wants to paint replicas of his work. Over the course of eight months, Nev develops rich Facebook relationships with his precocious fan, Abby, and her family, including her attractive mom, Angela, and her even more attractive 19-year-old stepsister, Megan.

Fostered by phone conversations and texting sessions, Nev’s feelings for Megan get very serious. So it appears, anyway, in the filmmakers’ depiction, which consists of supposedly candid footage of Nev and re-created online interactions.

Then Nev gets a clue that the blonde midwestern artist/dancer/songstress/horse farmer may not have been 100 percent honest with him. He and the filmmakers pay her a surprise visit in Michigan to find out what’s up IRL.

What they discover is intriguing and moving from a human point of view, but not especially shocking — at least not to anyone familiar with certain highly publicized cases involving self-presentation on the Internet.

Skeptical viewers of Catfish ask: Are people still naïve enough to believe what they’re shown online? Specifically, is someone like Nev that naïve? Did he and his brother and Joost fabricate his cyber-infatuation to create a marketable “documentary,” thereby forcing the drama’s other, less sophisticated players under a harsh spotlight? Or, some paranoids ask, is everybody in the movie a willing performer?

Who knows? These days, all Americans are potential reality stars. I can say, though, that certain people and problems in Catfish seem disturbingly real. And Nev’s gullibility, while perhaps played up for the cameras, is far from unprecedented. People, including hipsters, believe what they want to believe. That’s an axiom online and off.

Real, fake or halfreal, Catfish is an absorbing story and a reminder not to confuse the looking-glass world of social networking with face-to-face interaction. It’s also a scarier cautionary tale about Facebook than is The Social Network: If you haven’t checked your privacy settings, you will now.