United States Patent and Trademark Office awarded Amazon a patent for "Social Networking System." Amazon's reasoning throughout the whole process has been that, since they purchased PlanetAll in 1998, and PlanetAll is often considered to be the first social network on the Internet, Amazon itself is responsible for inventing the modern social network.
Here's an abstract of the patent:
A networked computer system provides various services for assisting users in locating, and establishing contact relationships with, other users. For e.g., in one embodiment, users can identify other users based on their affiliations with particular schools or other organizations. The system also provides a mechanism for a user to selectively establish contact relationships or connections with other users, and to grant permissions for such other users to view personal information of the user. The system may also include features for enabling users to identify contacts of their respective contacts. In addition, the system may automatically notify users of personal information updates made by their respective contacts.