That's true...if only new computers shipped without an operating system, and operating systems didn't come with a browser installed, and you had to turn on every feature in every application or website that you signed up for. If only the world was "off" by default and I had to spend lots of time and energy trying to get things into a usable state, instead of having the settings set to usable levels by default.
You might disagree with the defaults they've chosen, but having everything "off" by default isn't a great world.
I fail to see how the examples you provide have any parallels with the "opt in" by default settings in a social application.
Having everything by default is the very reason people chose to use this application in the first place. That's the product people bought into--with their data and attention--and now that product is getting changed, in many cases, without their knowledge and/or without their understanding of what's at stake.
You get raped by default unless you "opt-out". It's become a tradition. Because after all, where's the wrongdoing if you can opt-out, eh? Sometimes I hate the world.
You might disagree with the defaults they've chosen, but having everything "off" by default isn't a great world.