Facebook said it hit the 300 million member mark, giving the popular social networking site a user base that's roughly equal to the population of the United States.

"It's a large number, but the way we think about it is that we're just getting started on our goal of connecting everyone," said Facebook CEO Mark Zuckerberg, in a blog post Tuesday. The 300 million number represents worldwide users, so Facebook has plenty of room for growth—even in the U.S., where it counts about 90 million members.

Zuckerberg said improving the performance of Facebook—which is known for not infrequent glitches and temporary outages—is key to increasing the site's penetration.

"Because we want to make it easy and fast as possible for the world to connect, one of the things we think a lot about is how to make Facebook perform even faster and more efficiently as we grow," wrote Zuckerberg.

That means Facebook IT personnel may have to perform some heavy lifting behind the scenes. "We face a lot of fun and important challenges that require rethinking the current systems for enabling information flow across the Web," said Zuckerberg. "The ratio of Facebook users to Facebook engineers makes it so that every engineer here is responsible for more than one million users," he added.

Facebook is experimenting with a lighter version of itself with an eye to boosting performance for users who only want access to its most basic tools and services.

Facebook Lite went live last week in the U.S. and India. The company described the effort as an attempt to create a version that loads certain tools quickly and easily. Facebook said it plans to introduce additional features to Facebook Lite in the coming weeks and asked users for their feedback.

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