- <p>In addition to ad brokers, social media sites discovered they could get in on the action.
- A few years ago, the major social media sites like Facebook and Twitter convinced a large number of websites
- that it would be in their best interest to place little social media icons on their pages.
- These are not just images. They contain <a href="https://developers.facebook.com/docs/plugins/like-button/">embedded code</a> that links back to the social media site, and, among other things,
- loads a third-party cookie on the device. These cookies are placed even if the user does not have an account with the social media platform.
- Over time, companies like Facebook (which also runs an ad network) have built up quite a large number of detailed profiles about people who have
- <a href="http://www.theverge.com/2016/5/27/11795248/facebook-ad-network-non-users-cookies-plug-ins">never even created an account on their site</a>.</p>