Vitalik Buterin tells about how his views on privacy changed in recent years:
"I'm considerably more pro-privacy than I was a few years ago. A few years ago, my position was closer to "in a well-running society it's probably optimal that everyone sees everything, the value for privacy tech for ordinary people is (i) to let them buy weed, put up beds so people can sleep over in offices, and otherwise circumvent silly regulations, and (ii) to maintain a healthy balance of power, because even if more transparency is good, the government only having the all-seeing eye and everyone else being in the dark would give too much power to the government".
Things that changed my mind, and made me believe that even in a hypothetical perfectly equal and fair society people having some privacy is a good idea include:
Reading Robin Hanson and others' literature on signalling, and seeing just how large a portion of our lives it still is. Basically, I see privacy as a way to prevent signalling concerns from encompassing all of our activity, and creating spheres where we are free to optimize for our own happiness and just our own happiness, and not what other people think about us.
Having a deeper understanding of the ways that it's possible to make other people's lives suck even as a law-abiding private citizen, and realizing that privacy is an important self-defense tool for those situations.
Realizing more deeply that "the people" are not always virtuous, and that social pressure as a mechanism for influencing people's behavior doesn't always lead to results I approve of (see: recent string of internet mobs leading to people getting fired for political views). Realizing how bad mainstream media is even today, which makes me more understanding of people's desire to protect themselves from them.
Mass surveillance is problematic because (i) I don't trust governments and large corporations to have interests that are aligned with us, and (ii) it creates points of centralized data collection that could get hacked, leading to everyone getting that data even if that was never the original intention. That said, in the physical space it's pretty unavoidable, so we should at least work hard to make the internet a more privacy-preserving place."