The Internet can be a blunt and brutal place. It’s built on unruly mobs moving across the virtual terrain, digesting stories and leaving behind carcasses. But it is also one of the last vestiges of wide-eyed, unfettered belief.

The former describes how it is that the strange and elusive case of Manti Te’o is being efficiently dissected on the Web. The latter describes how it is that people online could love girlfriends who do not exist.

Te’o, a star Notre Dame linebacker and runner-up for the Heisman Trophy, had made the story of his leukemia-stricken girlfriend, Lennay Kekua, an essential part of his personal narrative. She had a photo on Twitter, and he spoke poignantly about their conversations and exchanges. After learning she died, he went out and made 12 tackles against Michigan State, or so the story goes. Except that she didn’t die. Because she didn’t exist.

Kekua was either Te’o’s creation — a publicity hoax — or someone else’s prank. Either way, the story unraveled when started pulling threads.

“To realize that I was the victim of what was apparently someone’s sick joke and constant lies was, and is, painful and humiliating,” said Te’o in a statement issued Wednesday evening.

Immediately, people began to question this explanation. Te’o had claimed to have known Kekua for three years. How could he have been duped for so long? And how could he consider her his girlfriend, when they had never met?

One of the interesting aspects of the Internet is the way that the veil of anonymity has come to provide a false sense of authenticity. On the Web site, one of the most popular features is “I Am A” in which users describe their unique life experiences — “I am a firefighter,” “I am a guy who had a heart attack today,” “I am one of the 50 wounded in the Aurora theatre shooting” — and invite readers to ask anything they want. Sometimes proof of identity is demanded, but often the willingness to be present and be vulnerable is accepted as its own evidence. After all, in an anonymous forum, with nothing to gain, why would someone lie?

“I think he got duped.” Nev Schulman knows something about being duped online. Two years ago, he was the subject of “Catfish,” a documentary that chronicled his blossoming relationship with a young woman on Facebook who lived a thousand miles away — and who turned out to be a fraud. Now “Catfish” has become an MTV show; he and co-host Max Joseph travel around the country helping lovelorn individuals figure out why their online paramours don’t want to meet in real life. The person behind the keyboard is never the one in the picture. The show is a lost-love story for our modern times.

Schulman and Joseph are tangentially involved in the Te’o case — Schulman received an e-mail last month, only recently discovered buried in his inbox, from someone claiming to be involved. She said her image was being represented as someone else’s.

Joseph speculates that it would be especially appealing for someone like Te’o — a promising young man navigating a world of fame and hangers-on — to find solace in an online-only relationship. The relationship could have been compartmentalized from the rest of his life. “You’re talking to someone in privacy,” he said. “They become this kind of isolated person for you to trust — it becomes easy to talk to them, and they’re always there.”

There is a widespread sense, perhaps untrue, that people can be most “real” when they are most hidden — that all of us are Cyranos who can only speak our true minds when our faces and names are invisible. It’s a lovely notion. But it makes us oblivious to flaming red flags: A gorgeous female Stanford graduate who says she loves you should want to meet you. And a linebacker whose fame skyrocketed because of his tragic personal history? Someone should check and see whether that history is true.

At its root, this was a story about the deep need to believe. What complicates that is that it’s not clear whether Manti Te’o wanted to believe in a beautiful, fake girlfriend or whether we wanted to believe in him.

The impulse obviously isn’t unique to the Internet — the rundown of never-was frauds sweeps back decades, including “Tony Godby Johnson,” whose middle-aged creator hoodwinked legions into believing she was an AIDS-stricken little boy. But the Internet has made it infinitely easier. Witness the 2011 story of Amina Arraf, a gay female Syrian blogger who was actually a straight American man.

This time, if the hoax was on Te’o, then the compartmentalized relationship has suddenly exploded, taking over the rest of his life and defining him as the man with the fake, dead girlfriend.

If the hoax was on us, then the gears of the Internet will continue to whir, ferreting out details of the betrayal and proving that, even if nobody knows you’re a dog online, someone is going to eventually find out.