Facebook has estimated that 83 million of its accounts are fake accounts, which could negatively affect its bottom line. Of these, Facebook estimated that about half were "duplicate accounts," or side-accounts that members maintained for their own reasons. The rest are spam and mis-categorized business and professional accounts. All told, the fake accounts make up about 8.7% of all Facebook accounts, although Facebook would not comment on how many of the friendships on Facebook were fake ...