We've known for years that the NSA likes to spy on foreign entities and after Edward Snowden leaked documents which pertained to some of the NSA's programs, we realized that US citizens may also be on the agency's list. Slowly but surely, we are finding out just how common it is for the NSA to spy on US citizens who may or may not have connections to foreign governments and organizations.
With more documents now leaking from the NSA, it has become clear that the NSA does indeed create social connection maps on its suspects which therefore puts thousands of other Americans in the NSA's database.
According to the New York Times, the NSA claimed that changing its policies to allow this type of social connection mapping was simply to connect the dots between foreign entities and US citizens who may be linked to terrorists.
However, the amount of data collected from these social maps is so enormous that there is no way that it is all coming from people that may potentially attack the United States. Many of the most recent domestic terrorists who were likely monitored by the NSA had hundreds of connections to innocent people. These innocent people now have to live the rest of their lives in the NSA's database simply because they had a lose connection to someone that did something bad.
NSA officials have refused to come out with statistics showing how many American citizens have been monitored by these efforts, nor have they been willing to release information on how many people are monitored despite not causing any harm to the US.
Although a lot of specifics were not provided in Edward Snowden's most recent documents, we now know that bank records, insurance information, Facebook profiles, etc are all used by the NSA to build the social maps.