Social networking invites major corporations to invade your privacy and sell your personal information. Have you ever posted a comment on Facebook, only to notice an advertisement appear with content related to your post? Facebook projects it will earn $3.8 billion in revenue in 2011. That's not bad for a free site. If Facebook and other social networking sites don't charge their members, however, how do they make so much money? They do it by selling the ability to specifically target advertisements. On social networking sites, the website isn't the product, its users are. These sites run algorithms that search for keywords, web browsing habits, and other data stored on your computer or social networking profile and provide you with advertisements targeted specifically to you. At the same time, you may be giving the site permission to share your information with outside sources unless you specifically generate settings that disallow them to do so. Participating in applications like Farmville may also be allowing outside vendors access to your private information.