six degrees patent
n. The informal name sometimes applied to a patent for a network database and system used in some social networking sites.
Abrams wasn't concerned that Pincus and Hoffman would overtake Friendster when they struck out on their own. But that feeling was put to the test this fall, after a small company claimed ownership of a patent for software connecting people through personal associates and put it up for auction.

The patent is known as the "Six Degrees" patent, after the famous theory that everyone on earth is connected by no more than six intermediaries.
—Joseph Menn, “The Personal Links of Three Social-Networking Sites,” Los Angeles Times, December 29, 2003
Now come Tribe and LinkedIn, sites started last summer, whose owners paid $700,000 in September to YouthStream Media Networks for United States patent No.6,175,831, also known as the "six degrees patent," which they consider the seminal social networking patent. It covers an online software platform that allows users to build relationship networks. Andrew Katz, a lawyer with Fox Rothschild who specializes in Internet intellectual property deals, said, "This is probably the pioneer patent out there." Mr. Katz, who said he had no financial interest in either Tribe or LinkedIn, added, "It should be taken very seriously by everybody in the industry because it is in the hands of people who have the means and the business acumen to enforce it properly."
—Teresa Riordan, “Idea for Online Networking Brings Two Entrepreneurs Together,” The New York Times, December 01, 2003
2003 (earliest)
YouthStream Media Networks, Inc., a Delaware corporation (OTC Bulletin Board: YSTM) (the "Company"), announced that effective September 23, 2003 it had sold its interest in U.S. Patent No. 6,175,831 entitled "Method and apparatus for constructing a network database and system", also known as the "Six Degrees Patent", and certain related intellectual property rights, including computer source and object code files, software assets and other digital assets, documentation and rights, to an unrelated party for a cash payment of $700,000.
—“YouthStream Media Networks, Inc. Announces Sale of Patent and Related Rights,” PR Newswire, September 29, 2003