According to Nielsen Online, social networks and blogs are
now the 4th most popular kinds of online activities. 67% of the world online
population are now visiting them and the time they’re spending on them is
growing by three times the overall growth rate of the internet. Social networks are now visited more
often than personal email is read.
http://www.smashingmagazine.com/2009/07/13/social-network-design-examples-and-best-practices/
