As Facebook takes steps to drive more real-time conversation, there's concern that it's losing its attraction for young users, who may be spending more time on Snapchat, Twitter, Tumblr and Instagram (which Facebook owns).
A recent report from iStrategyLabs found that the number of U.S. teens ages 13 to 17 on Facebook had fallen 25.3 percent from its 2011 report, while that of users 55 and older had risen 80.4 percent.
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Facebook, which is in a quiet period, said it does not respond to third-party studies but will disclose daily and monthly active user numbers with its next quarterly earnings, on Jan. 29.
The company pointed to statements from CFO David Ebersman and COO Sheryl Sandberg this past fall.
In the third-quarter earnings call , Ebersman said that there had been a slight downturn in its "youngest" teen users in the U.S., while total U.S. teen use remained steady (indicating an uptick among older users in that group).
Sandberg followed up on the stock's drop on that news, saying in an interview with AllThingsD, "I think the reaction to that comment has been blown out of proportion."
—By CNBC's Julia Boorstin. Follow her on Twitter: