Introduction: 6. LinkedIn LinkedIn is a business-oriented social networking service. Founded in December 2002 and launched on May 5, 2003, it is mainly used for professional networking. As of 2015, most of the site&#x27;s revenue comes from selling access to information about its users to recruiters. In 2006, LinkedIn increased to 20 million members. As of March 2015, LinkedIn reports more than 364 million acquired users in more than 200 countries and territories.