Mark Zuckerberg says Facebook will double in size every year (video)

 Mark Zuckerberg  returned to Harvard officially for the first time Monday, winning a warm welcome from the university where he created Facebook and embarked on a well-chronicled meteoric ascent.

It was clear Zuckerberg was no longer the dropout who left the iconic Ivy League institution, even if he still dresses in the classic campus uniform of T-shirt, jeans and sneakers.

If he weren't so famous, the billionaire and Silicon Valley entrepreneur portrayed as the flawed protagonist of the Oscar-nominated "The Social Network" could have passed for any one of the hundreds of computer science students who came to hear him speak.

"It didn't seem it was that different than talking to other Harvard students," said Kyle Solan, 19, a computer science major afterward. "He seemed very down to earth."

Just a few blocks from where he started the world's largest social network, Zuckerberg took part in a rare question-and-answer for students, who snapped up tickets to the event with the same frenzy reserved for favorite bands.

"We weren't originally planning this as a business or anything," Zuckerberg said sheepishly of the phenomenon that Facebook would become. "If I had a chance to do it again I would have gone to classes."

Zuckerberg's rock-star reception marked a sea change from when the entrepreneur famously landed himself in hot water for creating Facemash, a website that allowed users to rank their fellow students' attractiveness and an incident immortalized in the film.

Speaking at his usual machine gun clip, Zuckerberg appeared every bit as driven as the character Aaron Sorkin imagined for "The Social Network". But his bluntness and occasional humor in response to questions ultimately won the crowd over.

CODING THE CLASSICS

More comfortable with coding than the classics, Zuckerberg playfully acknowledged a lackluster academic career. Indeed, he said he once aspired to be a classics major, describing how he passed a course on ancient Rome while working on Facebook by building an Internet site for students to share notes.

"About halfway through the semester I stopped going to class," he said to laughter from the audience.

One day he sent around an email to other students saying: "Hey, I built a study tool for everyone. And everyone filled out all the answers of all the significance of each of the pieces of art work, and made it a lot easier to study and I passed!"

Zuckerberg's return was labeled his first official on-campus appearance since leaving in 2004, though he has been back informally. His creation Facebook has been a huge presence on campus since, to the consternation of its professors.

At least one Harvard professor, British historian Niall Ferguson, has warned students he will fail anyone he finds using the site during his class.

While Zuckerberg appeared for the most part at ease, he still lacked the polish of a seasoned executive at public appearances. Asked what books inspired him, he faltered and admitted he was "stumped" by the question. When another student asked what global problems worried him, he responded only by detailing different features on Facebook.

The Facebook founder conceded he had a lot to learn.

"You have to be willing to make a lot of mistakes," he said. "The story of Facebook, we made so many mistakes and continue to, every kind of mistake. I mean I knew nothing when I was getting started. I still know so little. I mean I am so young running a company of this scale."

In response to a question about Facebook's privacy policy -- an area of constant criticism for the company -- Zuckerberg said Facebook was better than many others which gathered data on unsuspecting users to target ads.

"People share so much information, put so much stuff into Facebook that how their data is treated is super important and we're constantly working on more stuff to make that more transparent," he said.

Zuckerberg also boldly predicted that the amount of content that people share on Facebook would double annually for years to come.

"If you project forward 10 years, each person will share about 1,000 times more things per day than they are now - 2 to the 10th is 1024," he said.

(Editing by Peter Lauria, Edwin Chan and Derek Caney)