"The NSA is allowed to collect records for individuals up to two times removed from targets, creating exponential growth in the total number of records. Without this “two hops” rule, the effectiveness of the program would be “greatly diminished,” according to Jonathan Mayer, a professor of computer science and public affairs at Princeton University."
The Center for Internet and Society at Stanford Law School is a leader in the study of the law and policy around the Internet and other emerging technologies.