Social networking accounts for one in every four and a half minutes of the world's internet browsing time – some 110 billion minutes per month - according to statistics from Neilsen.
The analytics firm said three quarters of global internet users visit social networking sites.
The number of visitors to such sites has grown nearly 24% in the last year, and the average visitor spends 66% more time on them than they did a year ago.
Facebook is now the third most visited brand of site online, with 54% of the world's internet population visiting it. The average user spends 6 hours per month on the site.
Brazil is by far the most prolific user of social networking sites, with 86% of the population doing so. Nielsen said this is because of the popularity of the Google-owned Orkut site, which is managed by Google Brazil.
Italy is in second place, with a reach of 78% of active users, followed by Spain with 77% and Japan with 75%.
The country which spends the most time on these sites is Australia, with an average of over 7 hours per month. In the US, Italy and the UK, users spent around 6 hours per month.
Facebook is more popular in Italy than in its three main English-speaking markets (Australia, the US and the UK), but only by a margin of around four percentage points. Italy is the biggest Facebook user at 66% of the web population, followed by Australia, the US and the UK.
France, Germany, Switzerland and Spain are also among the ten countries where Facebook use is most common.
The most popular brand online is Google, with 82% of the internet population visiting Google-branded sites. Google-owned YouTube is visited by 47% of internet users.
For Microsoft, the various non Microsoft-branded sites/services, including MSN, Windows Live and Bing, are visited by 62%, while 48% visit sites with a Microsoft banner.