The slide continues: In a new report cited in the Washington Post, only 45% of teens between 13 and 19 years of age use Facebook. The article warns that "teen whims are as volatile as Twitter's trending hashtags," but this trend is not new. Use has been rather steadily declining long before Facebook executives admitted the phenomenon in November 2013.

Are teens reading more books? Of course not. They are flocking to newer sites, such as Twitter and Instagram, which can both now claim a higher percentage of teen usages than can Facebook.

Discussion Starters:

• Should the trend worry Facebook executives? Why or why not?
• How does the changing demographic affect companies' presence on Facebook. What would you advise a company such as Abercrombie on its social media use?