The latest Snowden leak shows that since 2010, the National Security Agency has been creating sophisticated graphs of Americans' social connections.
Using the shedloads of data it has collected, it can tell who a person's friends are, their locations at certain times, their travel companions and other personal information.
Another NSA memorandum, dated January 2011, reveals the agency was told to conduct "large-scale graph analysis on very large sets of communications metadata without having to check foreignness" of every e-mail address, phone number or other identifier.
The agency was mix and matching communications data with public, commercial and other sources, including bank codes, insurance information, Facebook profiles, passenger manifests, voter registration rolls and GPS location information, as well as property records and unspecified tax data.
In fact, it is possible that the NSA knows more about foreign citizens than their own government does.
It is also possible that Americans have been caught up in the effort. After all, a lot of foreigners might know Americans and send them an email from time to time.
All this means that if you ever sell a stuffed toy to an American with dodgy connections, you could end up on a no-fly list or be strip searched when you take your family to Florida.