[Ed. – You can’t blame your Mom or your buddy Joe for posting references to you, or having you in their email contacts list. Something everyone needs to keep in mind is that Google, Twitter, and AMAZON are doing similar things. Amazon compiles at least as much data on you as Facebook. Jeff Bezos is not your friend. His whole business model is Big Data, and you’re the lab rat.]
Daniel Kahn Gillmor, senior staff technologist at the ACLU, discovered that, although he never joined Facebook or any other social network, Facebook has a detailed profile on him.
Facebook obtains information from those not on Facebook in two different ways: from other Facebook users and by tracking people who visit other sites on the web.
When people sign up for Facebook, they’re encouraged to upload their contacts to make it easier for Facebook to connect them with their friends. That allows Facebook to access personal contact information for people who never signed up for the platform or gave their permission to share their information. Facebook knows that these contacts are friends of the new Facebook user, and can start compiling additional details on these non-members.