Facebook crosses billion-user threshold

Highlights mobile business amid monetisation concerns.

Facebook passed the 1 billion user mark in September, after eight years in business and a bruising first four months in the stock market.

The social network, which listed on the Nasdaq on May 18, has acknowledged that a slowdown in new-user acquisition is inevitable as its worldwide reach expands.

About 45 million users joined Facebook between July and September 14, when it hit a million users.

Facebook won 54 million new users in the previous quarter, from April to June -- way down from the 102 million users who joined during the first three months of 2012.

In an interview on NBC's "Today" show broadcast on Thursday, CEO Mark Zuckerberg was asked by co-anchor Matt Lauer how, with a billion users, the company wasn't "killing it" by making money.

"It depends on your definition of 'killing it.' I mean, we are making billions of dollars," Zuckerberg fired back.

In its last earnings report, Facebook said revenue increased by 32 percent to $US1.18 billion in the second quarter. But that marked the slowest pace of quarterly revenue growth since the first quarter of 2011 - the earliest data available.

Founded by Zuckerberg in a Harvard dorm in 2004, Facebook took three years to reach 50 million users.

By 2010, that hit 500 million. But with Google launching its own social network and other services from Twitter to YouTube vying for Web surfers' time, the social network is keen to keep rolling out new products to keep its members engaged.

"The key, of course, is monetisation of those users," Hudson Square analyst Dan Ernst said.

Facebook has been working to address criticism over the efficacy of its ads, concerns about its mobile business and questions over growth in the past month, with Zuckerberg talking up the company's mobile prospects and hinting at new initiatives in search and e-commerce.

Zuckerberg said the company's new mobile ads were delivering better results for advertisers than its traditional ads on personal computers.

The company reported having 600 million mobile users, up from 543 million at the end of June.

"There's 5 billion people in the world who have phones, so we should be able to serve many more people and grow the user base there," Zuckerberg said.