Three months ago during Facebook’s Q2 earnings call CEO and founder Mark Zuckerberg assured investors that they didn’t have a problem with youth and teenagers. During their Q3 earnings call earlier this week Facebook CFO David Ebersam admitted that the social networking giant is in fact losing teenagers.

In July Zuckerberg told investors and reporters: “There has been a lot of speculation reporting that fewer teens are using Facebook,” he went on to say “But based on our data, that just isn’t true.”

Ebersam said on Wednesday that use by U.S. teens was steady overall between the second and third quarter but the company has seen a decrease in “daily users among younger teens”. Ebersam softened the blow by saying it’s hard to track usage from teenagers. Many of Facebook’s youngest users misrepresent their age because you need to be 13 years old to open a Facebook account.

Last week the Huffington Post ran data from Piper Jaffray’s semi annual report on habits of American teens. That data showed that Facebook had fallen as the most important social network for teenagers from 42% in the fall of 2012 to just 23% in the fall of 2013. Interestingly in this fall Twitter beat out Facebook with 26% and Facebook’s photo sharing social network Instagram, tied with the social network proper.

While the Huffington Post reports that Twitter was actually down a bit in the latest data, networks like Vine and Snapchat, which appeared in the “other” category are clearly on the rise.

So what’s the cause of this problem?

People have been talking about Facebook’s slide with teens for nearly a year. Some contribute it to the time it takes to post and interact on Facebook vs the mere seconds it takes to upload a photo to Instagram or SnapChat, or the six seconds it takes to put a video on Vine. Privacy conscious teenagers are also staying away from Facebook where their parents often have accounts as well. While blocking using Facebook’s privacy tools worked earlier on, parents have wised up so rather than allowing parents to “spy” on their activities some teenagers are steering clear of the social network.

To some, even Facebook’s age policy hurts them in the long run. Many tweens use Facebook, lying about their age in order to secure a free account. By the time they become of age to use Facebook the stigma around having an account early is gone. Facebook used to police this better but as the network has grown so has their inability to make sure that “13 year old” isn’t talking about their 5th grade PE class.