According to the analysis by Experian Hitwise,
Market share for social networks and forums visits:
Brazil – 18.9%
Singapore – 16.4%
U.S. – 15.4%
India – 14.0%
New Zealand – 13.9%
France – 15.1%
Australia – 13.1%
U.K. – 12.2%
Facebook gained in market share by 5% in the U.S. since last year.
The fastest growing social network in india is facebook.
According to Nielsen,
The average U.S. user spent 7 hours and 46 minutes on Facebook.
Source
Experian Hitwise