Giant social network Facebook has topped one billion active users, founder and CEO Mark Zuckerberg announced on Thursday, Oct. 4.

About 600 million of those are mobile users. The new milestone also sees Facebook's average age of users drop again, now pegged at 22 from the 23 average in July 2010, when the site reached 500 million users.

"If you're reading this: thank you for giving me and my little team the honor of serving you," Zuckerberg wrote in the announcement on Thursday. "Helping a billion people connect is amazing, humbling and by far the thing I am most proud of in my life. I am committed to working every day to make Facebook better for you, and hopefully together one day we will be able to connect the rest of the world too."

The social networking site has registered 140.3 billion friend connections, including check-ins and location-tagged posts, and its users have uploaded an impressive total of 219 billion photos. Since the fall of 2005 users have uploaded 265 billion images to the site, though the figure includes images that have since been removed.

Other stats for Facebook activity include 17 billion location-tagged posts, and a total of 62.6 million songs played about 22 billion times overall. In an interview with Bloomberg BusinessWeek, Zuckerberg expressed his great joy, but said celebrations were relatively low-key.

"Well, just everyone came together and counted down, then we all went back to work," Zuckerberg told the publication. "We have this ethos where we want to be a culture of builders, right?"

Next on the agenda, however, is not necessarily going for more members, but adopting a strategy to use the shared data more effectively. According to Zuckerberg, the new objectives may involve commerce.

"So for the next five or 10 years the question isn't going to be, does Facebook get to 2 billion or 3 billion? I mean, that's obviously one question. But the bigger question is, what services can get built now that every company can assume they can get access to knowing who everyone's friends are," Zuckerberg said in the same interview. "I think that;s going to be really transformative. We've already seen some of that in games and media, music, TV, video, that type of stuff. But I think there's about to be a big push in commerce."

Asked whether he wants to make a prediction of when Facebook will hit two million users, Zuckerberg highlighted the company's focus on mobile.

"The big thing is obviously going to be mobile. There are 5 billion people in the world who have phones, and a billion people using Facebook. There are actually already 600 million people using Facebook on phones, so that's growing really quickly. And as more phones become smartphones, it's just this massive opportunity."