By Jessi Hempel
September 22, 2011

By Jessi Hempel, senior writer

FORTUNE — Mark Zuckerberg took the stage today at f8, Facebook’s sort-of-annual developers’ conference, to the screaming affirmation of thousands of laptop-toting fanboys (and also a few women) and a live-streaming audience that surpassed 100,000. What began a few years back as a fringe festival for legit hackers has become ground zero for anyone interested in helping build the infrastructure of tomorrow’s Internet.

What’s changed? A year and a half after the last f8, where the “like” button debuted, Facebook has increased its users 40% to 750 million and eMarketer estimates it will double revenues to an estimated $4.27 billion. Zuckerberg has become the Robert Moses of his generation, building out not just an operating system for the web or a way to organize it — but the web itself.

As expected, Zuckerberg unleashed a dizzying number of announcements: He introduced a redesigned profile called Timeline; a new way to bring applications into the Facebook experience; and, an evolved version of the “social graph” — the web of personal relationships that users map out by connecting to each other. Perhaps most significant, the social graph lets businesses like music service Spotify or streaming site Netflix (NFLX) more deeply integrate their services into Facebook.

“Imagine expressing the story of your life,” Zuckerberg explained. “If the original Facebook was the first five minutes [of a conversation] and the stream was the next 15, what I want to show you today is the rest–the next few hours of a deep engaging conversation.” Expect Facebook, in effect, to become our living digital scrapbook and even, eventually, perhaps our fossil.

Zuckerberg spoke to an overflowing mass of entranced developers who aren’t kidding when they pronounce “f8” as “fate.” If his announcements seemed confident and disruptive enough to border on arrogance, consider that we’ve seen this two-steps-forward routine before: First, Facebook releases numerous significant redesigns and new features. Then, users cry foul, often voicing concerns over privacy. The company, finally, pulls back on its plan and makes tweaks while we all settle down and adjust, building out the new features quietly anyhow.

Anyone complaining about the redesign of the newsfeed earlier this week would do well to remember 2006 when a more youthful CEO rolled it out in the first place. A Facebook group called “Students Against Facebook Newsfeed” attracted 740,000 members and a website called for a daylong boycott of the site, causing Zuckerberg to issue his first letter of apology and alter privacy settings. But he didn’t back down on the core feature and it became the backbone for the social web. Now, the newsfeed might as well be an institution. And so far, Zuckerberg’s mad impulse to force feed us sharing tools has worked.

At the moment, it would seem there’s not much competition over who gets to control (and make money from) all of this sharing and connecting. In June, Google (GOOG) launched its new social product, Google+, to great fanfare and attracted tens of millions of sign-ups right away, but three months after launch it’s not clear people are actually using it. (The company just recently opened Google+ to the wider public, hoping for a surge of new users.) Twitter is growing fast, but its scope is more limited and it has had considerable organizational challenges. MySpace is, well, dead.

What’s more, as sharing becomes the dominant paradigm for how information is discovered and passed on, augmenting and in some cases replacing traditional search, web sites that choose not to integrate with Facebook increasingly occupy overlooked corners of a shadow web. Those that embrace these tools early can gain competitive advantage; the lucky few that develop alongside the company as launch partners receive huge boosts. Daniel Ek, CEO of Spotify, took the stage alongside Zuckerberg to show off the music service’s new super ap. The bullet points above his head read, “More music, more variety, twice as likely to pay.”

As the web expands beyond our computers, this puts Facebook everywhere — as the dominant interface to our lives. As CEO of large digital ad agency AKQA with clients like Audi and Nike (NKE), Tom Bedecarre is thinking about a future in which Facebook is available on our TV sets and in our cars (voice-activated, of course). Says Bedecarrre, “For large marketers, Facebook is becoming the web.”

But it’s not a given that the web belongs to Facebook. These new changes are significant enough that they are sure to inspire intense reactions from users who may feel overexposed or simply overwhelmed by so much change. (Recent incremental changes to the site’s interface have already significantly changed the way the site looks.) The potential for competition isn’t limited to large social properties — any fast growing web property poses a threat. And that’s if Washington doesn’t step in at some point over privacy or concerns about competitiveness.

Maybe that’s why, as Zuckerberg’s audience grows, he makes more of an attempt at humility. He began this year’s event by inviting Saturday Night Live Star Andy Samberg up to make fun of him. “How many users does Facebook have?” Samberg joked. “Even more people than claim they invented Facebook.” It was self-deprecating. It was funny. For a moment.

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