True online privacy and anonymity would allow unrestricted self expression and freedom. The commonly perceived false sense of anonymity online (despite how fake) allows people to express their thoughts, opinions, feelings, ideas and concepts with less fear or judgement. It allows discussions that otherwise wouldn't exist if people were forced to show their real identity and photo on everything they wrote. Although we might as well have our real name and photo next to our reddit comments, since we aren't anonymous like we might think. Let me give an example. Maybe someone has a problem and would like to discuss it privately with other strangers online. There are many forums where people can go to vent and talk about their life problems without fear of judgment. This could be beneficial for someone who might be dealing with depression or suicide thoughts and doesn't want to sit face to face with a therapist. Maybe online privacy could even save somebody's life. Except that it doesn't actually exist, any chance of true privacy has been destroyed in exchange for a blurry notion of safety and security.

I'm more afraid of the people handling everyone's data than terrorists. IMO no human being (or giant group of them, for the matter) is flawless or trustworthy enough to be given that sort of power. There's also no telling what could happen to these databases at any point in the future, or who could get their hands on them. If these agencies were a single person, they could be charged with intellectual property theft on a massive scale for stealing digital works (i.e. private photographs and videos) from people without their consent. Since they take the approach of storing any data they can get, the majority of what is stored is harmless private data, not even necessary for national security purposes. It might not be so bad if they at least gave law abiding citizens the chance to take back some of their data and delete it from their databases, or vowed to permanently erase data taken from law abiding citizens after they die, but currently nobody (except perhaps employees) can even see what's stored on them. Until something is done to resolve or even address these problems, it's only sensible to be concerned about where the future is going to lead with this.