Facebook struck agreements allowing phone and other device makers access to vast amounts of its users’ personal information. The ultimate reasons for smartphones and other Internet-connected gadgets to strike agreements permitting them access to Facebook’s user information.

Who has the access?

Facebook has reached data-sharing partnerships with at least 60 device makers including Apple, Amazon, Blackberry, Microsoft, and Samsung. Over the last decade, Facebook apps were widely available on smartphones, company officials said. The deals permitted Facebook to exceed its reach. Also, allowed device makers offer customers popular features of the social network such as messaging, “like” buttons and address books.

Facebook officials defended the data sharing as consistent with its privacy policies, the F.T.C. agreement, and pledges to users. They said its partnerships were governed by contracts that strictly limited use of the data. It also includes any stored on partners’ servers. The officials added that they knew of no cases where the information had been misused.

The company views its device partners as extensions of Facebook, serving its more than two billion users, the officials said.

“These partnerships work very differently from the way in which app developers use our platform,” said Facebook vice president. Unlike developers that provide games and services to Facebook users. Also, the device partners can use Facebook data only to provide versions of “the Facebook experience,” the officials said.

Facebook’s view that the device makers are not outsiders lets the partners go even further. They can obtain data about a user’s Facebook friends. Even from those who have denied Facebook permission to share information with any third parties.

Several former Facebook software engineers and security experts said they were surprised at the ability to override sharing restrictions. They added, regardless of where the data was kept, it was governed by strict agreements between the companies.

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