Imagine a large cylinder shaped chamber. It's roughly 50 meters in diameter, and 30 meters tall. In the center is a guard tower, and on all sides of the room are prison cells. There are four levels of cells, and they are arranged so that the each cell can be observed by the guard tower.
This is the traditional design of a panopticon, a prison layout designed by Jeremy Bentham in the late 18th century. The purpose of the design is to allow for a single guard to observe all cells of the prison. While the guard cannot see every cell at once, the prisoners cannot see the guard through the glass and as a result must act as though they are being observed at all times.
The parallels to surveillance today are obvious. Just as the prisoners censor their actions because they know they could be under observance, a citizen may censor their actions to be more conforming to the state of government. This may mean not going to the Black Lives Matter protest, or not criticizing the president online. Its direct consequence is self-censorship.
Change in a society comes from the bottom up, and surveillance is an extremely effective censorship tool. Even if the intelligence collected is never acted upon, the knowledge of its very existence is sufficient to stifle dissent. We are all prisoners in our cells, so hide behind your sheets! We must all do our part.