Facebook rolled out Facebook Exchange, a program that allows advertisers to offer real-time bids for targeted ads aimed at users that have shown interest in a specific product or type of product online. When Facebook drops a cookie on its users, it tracks what they do when they leave the social network, including any products they may look at on search engines or e-commerce sites. It then shares this information with advertisers, and if they have something similar to offer, they can bid on the chance to show that user their ad. In other words, unless a user logs out of Facebook after each visit, anything they do on the Internet could potentially make them a highly sought after target for advertising.