On Thursday, Facebook celebrated its sixth birthday and surged to 400 million users. By all accounts, the site has come a long way. After weathering privacy disputes and redesign revolts, it surpassed MySpace in 2009 and became the most popular social networking site in the world. This merits a retrospective of Facebook's evolution.

First, Charles Petersen at The New York Review of Books marvels at how primitive Facebook used to be. The site's limited features made customizing profile pictures and user "Interests" exceedingly important:

If a social network profile was an online "home," then a Facebook page, in the early days, looked like a room in a recently constructed dorm: you might put up a raunchy poster or fill the shelves with favorite books, but the layout and the furniture remained exactly the same for everyone. ...

Instead of photos of themselves, early members often chose works of art or album covers or portraits of writers; those who included a personal picture rarely chose the most attractive, attempting, through a drunken photo or a candid shot, to convey an attitude of nonchalance. The list of "Favorites" was the occasion for particular anxiety and comedic juxtaposition, as Beethoven might share space with contemporary pop groups like OutKast or, more ironically, commercial schlock like Celine Dion.
For a less sociological reflection on Facebook's existence, tech blogger Sinha appraises Mark Zuckerberg's business savvy. She believes the founder's genius lies in not listening to his users. Every time Zuckerberg redesigns the site, users threw a fit. But Facebook's dominance shows that Zuckerberg may have known his users better than they know themselves. She cites tech blogger Vibhushan:
Zukerberg knows his customers. Zukerberg knows why his users come to the site, and also at the same time perfectly understands why they would stay with Facebook. There is always a resistance to any change (whether good or bad), and when it is change to something as routine as Facebook has become for millions across the world, it was bound to create some noise. –