Earlier quoted context omitted.
"The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause , supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."
Playing Devil's advocate here. The government position is that it isn't a search until they subject the data to analysis. Nor is it a seizure when you still have your data. Thus they draw a line between collecting data (making sure they have it) and actually searching it. Therefore broad data collection does not violate the 4th so long as they always get specific warrants before actually searching that data.
Why have no accountability and no transparency if they were not going to violate our privacy? I'm flipping the "If you have nothing to hide" bit on them.
But even if there were oversight, the main issue is the potential for abuse. Having all that data in the hands of an entity that can imprison you is a pretty frightening idea. Sure, maybe they're following the rules now, but in desperate times, people can behave immorally and radically. Do not trust other human beings, even if they are under the umbrella of "government". Look at what evil humans have done in the last century alone and you'll agree that we should limit the potential for abuse as much as possible.