The major problem with mass surveillance is asymmetry:

Whenever governments get additional power to track what citizens do (and ultimately think), citizens need to gain an additional degree of transparency regarding its government [0], so the system keeps its balance. If that does not happen - and obviously the opposite is the case for a very long time now - the degree of abuse of the new power imbalance will continue to increase, at the cost of the citizen.

[0] (This is something the President has emphasized, but his actions have, as we must expect from every politician, gone in the opposite direction - including the persecution of whistleblowers.)