According to a report released by Nielsen today, the total time spent on social networking sites by users worldwide grew more than 100% over the past year, as Facebook and Twitter posted massive gains in unique users.
Traffic to Facebook.com was up 69% year-over-year through March, while Twitter saw a 45% increase in site traffic during the period.

Globally, the total minutes spent on social networks monthly saw a more than 100% gain over the same time last year, driving the average time per person spent on social networks to over six hours per month.

View the report at http://blog.nielsen.com.