It's somewhat like the difference between going to a party at a friend's home (FB) and going to a party at a bar (here). You may see some of your friends at the bar but there are others you don't know and wouldn't want to be friends with if you did know them. Since many of the people at the bar don't know you and you don't know them, they will say things your friends wouldn't.
Social media use is also shifting significantly to mobile — nearly 40 percent of social media users access social media content from their mobile phone.
Nearly all social networking sites skew female, except LinkedIn. On Facebook, 62 percent of page views are from females.
Tumblr is an emerging player in social media, nearly tripling its audience from a year ago
Internet users over the age of 55 are driving the growth of social networking through the mobile Internet.
70 percent of active online adult social networkers shop online, 12 percent more likely than the average adult Internet user.