Often, Facebook knows non-members surprisingly well: People talk about strange happenings concerning the social network Facebook. A reader that does not have an account reports that he has received a Facebook invite mail from a friend. Among others, it contained a suggestion list with Facebook members that the recipient might know. Shockingly, the reader did know nearly all people in that list, but his friend who had invited him didn’t. For some of the contacts, they could not even be linked by a detailed web research.
But how does Facebook accomplish this? Facebook is also collecting data about non-members—with the aid of the members. For example. the Facebook App for iPhone offers to send all contacts available in the cell phone to Facebook: “When you enable this feature, all your cell phone contacts (name, e-mail address, phone number) are sent to Facebook.” Additionally, when you set up a new account, Facebook offers to look through your e-mail account to find friends on Facebook. Upon entering your e-mail address and the corresponding password, Facebook checks your contact list. Here as well, Facebook keeps note of the addresses.
“Just like any other web address book, Facebook stores the uploaded contacts,” the company explains. For the provider, that’s a service: “When users upload contacts and send out invitations, they want to be informed when their friends register.” Furthermore, friends that are not members in the platform, can be informed about events. “The e-mail addresses are necessary to make this possible.” Hereby, Facebook thinks that you yourself are responsible for your data safety: “It belongs to our service to store these data until the user that uploaded them removes them. Behind the question mark icon, we explain how an entry can be deleted and link to the corresponding page in the privacy terms.”
It is also possible that Facebook gets a link between a user and a non-member differently—for example when the first one searches for the name of the latter one, or if both have something in common, for example the home city, the school or the employer. However: Facebook does at least know the e-mail addresses of non-members. Until Facebook changes their privacy model, you have to take care yourself about removing the e-mail addresses of friends that you uploaded once. You can delete them on a well-hidden page.
Social network service providers are not the only companies with deep insights into the social networks of their users. Mobile service providers have insights into the social links of their customers, too. For example, the network supplier Comverse talks publicly about its innovation: to create a report about the perfect marketing for the social graph of the mobile phone users.