Facebook's Fine Print Includes Permission to Track

In order to access Facebook, users must agree to a lengthy terms of service contract that outline everything Facebook has permission to do. That includes tracking users, even when they aren't on Facebook, for advertising purposes.

Facebook tracks users by placing a cookie, or a small text file, on the computers of its users. The cookie communicates with so-called pixel code installed on many popular websites. Pixel code is often included in Facebook services that allow companies to take advantage of Facebook in several ways. Online publishers can install "Like" and "Share" buttons on content. Those buttons increase sharing on Facebook, which increases traffic to publishers' sites. Online retailers can use pixel code to purchase Facebook ads targeted to people who were just about to buy something, then got distracted and later ended up browsing Facebook.