Even though the people being spied on are often totally innocent, the government stores their information for a very long time

TheAtlantic

The U.S. surveillance debate is constantly distorted by the fact that national-security officials hide, obscure, and distort so much of what they do. Occasionally a journalist is able to expand the store of publicly available information, most recently thanks to Edward Snowden's indispensable NSA leaks. But even public information about government surveillance and data retention is difficult to convey to a mass audience. It involves multiple federal agencies with overlapping roles. The relevant laws and rules are complicated, jargon is ubiquitous, and surveillance advocates often don't play fair: They use words in ways that bear little relation to their generally accepted meaning, make technically accurate statements that are highly misleading, and even outright lie, as Director of National Intelligence James Clapper did before Congress. 

Their distortions continue in part because no matter how many times President Obama, NSA Director Keith Alexander, Clapper and others egregiously mislead the public in their statements about surveillance, news organizations treat them as honest men and report on subsequent statements as if they're presumptively true. For all these reasons, journalists who take the time to understand the truth and the way government officials are distorting it find that their work has just begun. They need to find comprehensible ways to explain complicated distortions, even as more hard to understand information becomes public each week. Absent this asymmetry, surveillance-state critics would be in a much stronger position. 

Enter a new report published by Brennan Center for Justice at New York University Law School. "What the Government Does With Americans' Data" is the best single attempt I've seen to explain all of the ways that surveillance professionals are collecting, storing, and disseminating private data on U.S. citizens. The report's text and helpful flow-chart illustrations run to roughly 50 pages. Unless you're already one of America's foremost experts on these subjects, it is virtually impossible to read this synthesis without coming away better informed.

The text gives detailed answers to questions like, "What does the NSA do with all the emails and phone calls of American citizens that it collects?" Then the information is summed up in graphics like this one: