Apple supposedly included Facebook integration in an early build of iOS 5, but it didn't make it into the final build because of failed negotiations between the two companies. Facebook integration was built into iOS 6.
9to5Mac, which originally reported the story, says iOS 7 users will be able to post content directly to LinkedIn via a share sheet. Apple has already announced LinkedIn integration for OS X Mavericks, so it would make sense to see similar integration in iOS 7.
Article Link: Apple Planning LinkedIn Integration for iOS 7