There was always a line though between "i'm sharing this personal information with you privately" (i.e. registering with your name and e-mail address), and "I'm sharing this information with the general public". You also were able to remain somewhat anonymous, by registering with your real name but making sure other users only saw your screen name.

While there was always the threat of someone finding your publicly shared photos or stories and using them for nefarious purposes, the idea of the company you're giving them to analyzing all of that private and public data, across the entire web thanks to tracking cookies, and using it to manipulate you or packaging it up and selling it was never really a concern. No one had the capabilities to analyze that much data 10-15 years ago, and if they did it wasn't yet profitable.

The idea that you now have zero control over how your personal and private data is used, or who it's sold to, is terrifying.