From Fast Company
Enter Facebook. The social network is partnering with Nielsen to provide the demographic data on who sees ads placed around the Internet–even if those ads aren’t placed on Facebook itself–sort of like a real-time, always-on Nielsen family.
Here’s how it works: Advertisers tag their ads and then place them on their targeted sites around the web. When the ads are viewed, the ads make a call to Facebook, which then searches its own user database to identify the viewer of the ad. It then gathers up that person’s demographic information (but not personally identifiable information) and sends it to Nielsen. Nielsen is then able to report back to advertisers who saw their ads in a particular campaign.
Facebook Is The New Nielsen Family | Fast Company.
