More than two-thirds (67%) of the global* online population visits social networks and blogs, and participation in these “member communities” is now the fourth most popular online category – behind search, portals, and PC software, but ahead of personal email use, according to research from Nielsen Online (via MarketingCharts).

Use of member communities is also growing twice as fast as any of the other four largest sectors, and three times faster than the overall internet, states the “Global Faces and Networked Places” (pdf) report.

Social networking and blogging now account for nearly 10% of all time spent on the internet and have “become a fundamental part of the global online experience,” said John Burbank, CEO of Nielsen Online.