It has more than 64 million users, brings in around $100 to $150 million in revenue annually and, based on an investment by Microsoft last fall, is worth $15 billion. At the very least, it's allowed the world to know that The Four Obsessions Of An Extraordinary Executive by Patrick Lencioni is one of Mitt Romney's favorite books.

This could be called graduating with honors.

Four years ago today, on February 4, 2004, went live. (Here's a screenshot of the site's welcoming page when it was eight days old.) That makes this as good a day as any to celebrate Facebook's college graduation, and, like any good commencement speaker, to take stock of where Facebook came from, and where it might be going.

The first press the site ever received was a write-up in The Harvard Crimson on February 9. Founder Mark Zuckerberg ("Mark E. Zuckerberg '06," per the Crimson's style guide), told a reporter that he'd spent about a week coding the project. He didn't see what the big deal was, really. College administrators had been talking about launching an online directory with student ID photos for several months, but it seemed to be taking too long. Tired of waiting, Zuckerberg just did it himself. "I'm pretty happy with the amount of people that have been to it so far," he said, just days into the experiment. "The nature of the site is that each user's experience improves if they can get their friends to join it."

Since that innocent time--though a certain incipient smugness is already detectable in Zuckerberg--most everything he said or wrote or accidentally forgot to delete from an online diary while starting Facebook has been parsed in federal court, due to ongoing legal proceedings related to the origin of the site. 

I was a senior at Harvard when Facebook mania swept the campus. First Harvard, then other Ivy League schools, then all U.S. colleges, and now high schools, workplaces, the rest of the world--all are jumping into the social world that Zuckerberg created. I had a unique vantage point, watching the first domino fall, and, already, trying to make sense of it. Less than two months after Facebook's creation, the Crimson's weekend magazine, Fifteen Minutes, which I used to edit, had the dubious honor of publishing the first trend story about it. ("Ever since sprung into the Harvard collective consciousness like a Trojan-horse virus, thinkers have been analyzing the social implications of the website's success.") And, of course, I joined the site, too. How could I not?

But why was Facebook instantly so popular?

I suspected at the time that Harvard, where Facebook was incubated, was a particularly welcoming environment for a product that allows social interaction via mouse clicks in lieu of shared verbal pleasantries. Most of the 6,000 or so undergraduates live on campus. Students would continually find themselves in large classes, libraries, and dining halls, or at parties and local bars, with a cross-section of fellow students who looked vaguely familiar. What a gift to track down and catalogue these outliers of one's social orbit! Of course, as it has taken off all over the world, it's become clear that the desires Facebook fulfilled are not unique to some of the most socially awkward college students.

One take, proposed by Zuckerberg himself, is that the universal appeal of Facebook lies in the "social graph" theory. The idea is that people trust their friends and friends of friends and are interested in how paths intersect. Zuckerberg's idea seems rooted in name-game-filled conversations from the early days of college, when even a tenuous connection could greenlight a friendship. A less generous reading of Facebook's success would be that people enjoy displaying their carefully curated selves and social networks like an accessory.

I think the best way to address Facebook on the occasion of its graduation is to hand the podium over to another famous Harvard dropout, Bill Gates. Gates gave the college's commencement address last year, and he mused about the social lives of undergraduates. "Dorm life was terrific," Gates said. "There were always lots of people in my dorm room late at night discussing things, because everyone knew I didn't worry about getting up in the morning. That's how I came to be the leader of the anti-social group. We clung to each other as a way of validating our rejection of all those social people." (Those validation sessions might look dramatically different today, when people are less likely to stay up all night in a dorm room "discussing things" than they are to sit in front of a laptop toggling between work and play to update their Facebook status.)

The main thrust of Gates's address was about his philanthropic work. He talked about how he managed to leave college without fully understanding the inequalities in the world, and how he's slowly come to understand how challenging it is to eradicate a scourge--say, high rates of child fatalities due to treatable infectious disease--if it's a tragedy the market tolerates. His message is simple: Take action, kids. Pull your head out of the sand earlier than I did. You have the technology to do so. One point he stressed was the power of the Internet to effect change. "The magical thing about this network is not just that it collapses distance and makes everyone your neighbor. It also dramatically increases the number of brilliant minds we can have working together on the same problem--and that scales up the rate of innovation to a staggering degree." Zuckerberg used the same logic when he opened up Facebook to outside developers, letting anyone create "widgets" on his own network.

But has Facebook taken "on the big inequities," as Gates urged in his speech?
A "causes" application and other awareness-raising groups do indeed connect thousands of people with common interests in humanitarian efforts. And it's very easy for people to organize races for cures and alert their 547 nearest and dearest to articles on under-covered international tragedies. But, most significantly, Facebook is smack in the middle of the 2008 election: sponsoring the pre-New Hampshire primary debates, becoming ubiquitous for candidates (though some have better profiles than others).

Tomorrow will offer a powerful example of the potential impact of Facebook. On America's most Super Tuesday yet, Facebook users will be organized. They have invited each other to viewing parties and friended their favorite candidate, trading notes on debate performances and inspirational rhetoric. They will carpool to the polls and check their polling place on the Facebook page of their secretary of state's office.

And what might Zuckerberg say four years later, with roughly two million new

users from around the world joining each week? Reflecting over the site's four years of existence, maybe he'd echo what he said after just a handful of days. "I'm pretty happy with the amount of people that have been to it so far."

Rachel Dry is an assistant editor at The Washington Post.

By Rachel Dry