Twitter to start including videos in tweets from Vine: http://mashable.com/2013/01/23/twitter-vine-videos/
LinkedIn's fastest growing group is Social Media Marketing: http://www.prnewswire.com/news-releases/fastest-growing-group-on-linkedin-is-social-media-marketing----international-trend-in-social-media-fueling-the-growth-188204151.html
Now, the Facebook news:
Facebook's mobile app was the US's most popular in 2012: http://www.comscore.com/Insights/Blog/Facebook_Vaults_Ahead_of_Google_Maps_to_Finish_2012_as_number_1_US_Mobile_App
Personal analytics for Facebook, by Wolfram Alpha: http://blog.wolframalpha.com/2013/01/23/introducing-expanded-personal-analytics-for-facebook/
Finding humor in Graph Search queries: http://actualfacebookgraphsearches.tumblr.com/
Can you kill your Facebook addiction? http://www.dailydot.com/society/facebook-addiction-faddict-30-day-challenge/