It would seem that Facebook would need to hault it's operations based on a newly awarded patent by the United States Patent and Trademark Office to Amazon. The patent generally outlines a text-book description of the type of "social network" that Facebook and so many other companies have build businesses upon.
The synopsis outlines a computer system that "provides various services for assisting users in locating, and establishing contact relationships with, other users" and that "selectively establish contact relationships or connections with other users" and enables users to "identify contacts of their respective contacts."
The patent was filed by Amazon in May 2008.