The social network's meteoric rise suggests that the open Internet isn't as appealing as a more controlled environment.
Facebook now has 500 million active users, the company said on Wednesday.
"This is an important milestone for all of you who have helped spread Facebook around the world," said CEO Mark Zuckerberg in a blog post. "Now a lot more people have the opportunity to stay connected with the people they care about."
"Active," as Facebook defines the term, means the user has logged in at least once in the past 30 days.
The milestone confirms what pretty much everyone already knows: Social networking isn't simply a fad; it's an increasingly valuable way to organize online communication and information.
The forthcoming movie about the founding of Facebook, The Social Network, anticipated the announcement. Its tag line reads, "You don't get to 500 million friends without making a few enemies."
Certainly, Google is worried that Facebook's closed network will exclude it from a large and growing segment of Internet interaction. The company is reportedly working on yet another social networking initiative known as Google Me to compete more effectively against Facebook.
To mark the occasion, Facebook has launched an application called Facebook Stories, which allows users to share a post with everyone using the application, rather than just friends.
So far, the stories seem to focus on how much users love Facebook. It remains to be seen how more negative viewpoints will be handled.
Choosing to use Facebook Stories means sharing your basic information, such as your name, profile picture, gender, networks, user ID, list of friends, and any other information you've shared with everyone, your birthday, and your current city.
Such sharing alarms privacy advocates and precipitates periodic privacy crises at Facebook. But it appears to have done little to dissuade people from using the service.
Google in the Enterprise SurveyThere's no doubt Google has made headway into businesses: Just 28 percent discourage or ban use of its productivity products, and 69 percent cite Google Apps' good or excellent mobility. But progress could still stall: 59 percent of nonusers distrust the security of Google's cloud. Its data privacy is an open question, and 37 percent worry about integration.