- <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 there 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>