Facebook has updated its policies for third-party application developers in a bid to explain why Twitter's new Vine video-sharing app is unable to access Facebook's friend-finder tool.
While the updated policies don't mention Vine by name, the biggest changes appear designed to explain why Facebook decided to block the app, a move that sparked a wave of criticism this week.
In a blog post Friday, Facebook's Justin Osofsky, director of platform partnerships and operations, said the "clarifications" were published after the site received questions about its policies over the past few days.
"For the vast majority of developers building social apps and games, keep doing what you're doing," he wrote. But a "much smaller number of apps" violate its policy by using Facebook to "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."
Vine, which is owned by Twitter and launched Thursday, includes a tool that allows users to search for their Facebook friends and add them to their Vine network. Vine also lets users automatically share the videos they create with the app with their Facebook friends -- a function that remains intact -- as well as with their Twitter and internal Vine connections.
Controversy broke out when users discovered later on Thursday that the Facebook friend-search tool had been disabled. Facebook has yet to say whether it intentionally blocked the feature, but the clarified policies it published Friday explain where the site stands on matters related to competitors using its social graph.
One of the amended sections reads: "You may not use Facebook Platform to promote, or to export user data to, a product or service that replicates a core Facebook product or service without our permission." The policies don't say what, exactly, constitutes a "core" Facebook product.
The new policies retain similar language about permissions, but give additional guidance about data-sharing with third-party apps. On the topic of reciprocity, for instance, the policies say developers can build their own social network via Facebook's API (application programming interface), but only if the app allows users to share their experiences back with Facebook users. Vine does offer this functionality.
Asked whether Facebook blocked the search tool or if there was a technical issue on Twitter's end, Twitter has said it has no comment beyond the error message users get when they try to perform the search.
The new guidelines also say that if Facebook disables an app, the developer of the app must delete all the user information it collected through Facebook's API, unless it is basic account information or it receives consent from the user to retain it.
Finally, the policies clarify that developers are responsible for "providing users with a quality experience and must not confuse, defraud, mislead, spam or surprise users."