Back in 2001 and 2002, a Dutch programmer named Joannes Jozef Everardus Van Der Meer applied for and received two U.S. patents related to social networking. Van Der Meer has since died, but his family is now suing Facebook because they say the social network's "Like" button infringes on those patents.
The first patent, No. 6,415,316, describes a Web page "diary," which would allow users to share third-party Web content with a select group of people. The second patent, No. 6,289,362, describes a method for transferring content to those diaries by clicking buttons on Web page--a functionality remarkably similar to Facebook's Like button.
Mark Zuckerberg founded the website that would become Facebook in 2003.