Vine has been cut out of Facebook — at least in part. The new app, which was designed by a Twitter-owned company, limits you to six-second bursts of film creativity and carries a menu option to find friends who are using Vine on its network. But when users tap their screens to find kindred spirits on Facebook, all they get is an error message.

“Vine is not authorized to make this Facebook request,” the message says.

When asked about what, exactly, is keeping Vine from getting this authorization, a Facebook spokesperson pointed to a company blog post written Friday that aims to clarify its developer policies. In particular, the company pointed to the part of its policies that say apps cannot duplicate any network “core functionality.”

“Our goal is to provide a platform that gives people an easy way to login to your apps, create personalized and social experiences, and easily share what they’re doing in your apps with people on Facebook,” wrote Facebook’s director of platform partnerships, Justin Osofsky. “For a much smaller number of apps that are using Facebook to either replicate our functionality or bootstrap their growth in a way that creates little value for people on Facebook, such as not providing users an easy way to share back to Facebook, we’ve had policies against this that we are further clarifying today.”

Facebook declined to comment on whether it believes Vine’s app duplicates any central part of its product.

Vine, released Thursday for the iPod Touch and iPhone, has climbed the charts in Apple’s App Store, cracking the list of the top 20 most-downloaded apps.

Some people have criticized the platform for posting all videos made on the network publicly, and not allowing users to simply share their quick thoughts with a select number of people.

NBC News’ Rosa Golijan wrote Thursday that she would like a way to block or report users who use the app inappropriately.

She said that while Vine does allow users to delete comments from their videos, she would like to see the ability to limit visibility from the start.

(Washington Post Co. Chairman and Chief Executive Don Graham is a member of Facebook’s board of directors.)

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