Teens don't want to spend their time on Facebook anymore. Why? There's a couple of big reasons: 1) Mums are on FB and kids don't want to be in the same space as their parents, 2) They don't have time to compose written messages and engage in conversations, they would rather share photos or videos on Instagram or Vine. (VIEW LINK)
I heard many years ago that Billabong wasn't fashionable for teens as Dad's started to wear it... similiar to point 1!