Of course still popular in terms of traffic for teens, currently Facebook is 2nd to Twitter among teens in terms of importance. Waning importance for teens is translating into lulls in traffic. Myspace, in 2012 less than 7% of the teens found it important, has now dropped out of the picture. Google+ is, hard to say what is happening…
See: Statista 2013 and Statista 2012 for more