I suspect from details in the article that the leak is from the external parties, probably former employees of the external parties: - Facebook employees would

I suspect from details in the article that the leak is from the external parties, probably former employees of the external parties: - Facebook employees would not call that number “friend link”: it has another name internally; “friend link” sounds like how you’d explain it to someone who’s not familiar with graph theory; - the WSJ is anything but exacting, but the article is oddly vague on when the program was terminated. That sounds out-of-character, unless the source left since, and couldn’t confirm if the program was maintained.