There are always different levels of privacy. Everybody knew Google was "reading" their emails. The understand of that was never that Google will expose your individual email to a company. Similarly people understood that Facebook used the data about them to monetize and advertise to them. I don't think anyone assumed they'd let someone else literally take that data.
I've always been incredibly suspicious of the way Facebook handled it's user data. Remember back when every website on the internet had a box that showed "random" people that liked their website, and if you had any friends that liked it, they were in there?
How about all of the services using Facebook OAuth that subtly leak social graph information? For exactly this reason, Facebook OAuth is always my absolute last resort, and I'll almost always skip a service entirely if it's the only option.
Still, I always gave Facebook the benefit of the doubt and I figured that these things were handled by Facebook directly as a "plugin" to the app/website (I'm not a web developer, I don't know the details of how this would work), and the various services didn't actually see the data. It's pretty mind blowing to me that this is not actually the case. I always felt I was being absurdly paranoid about Facebook compared to most people I knenw, now it turns out I was not being even remotely paranoid enough.
Does anyone know if Google is similarly aggressive with user data sharing? I've never noticed information leakages similar to the above coming from Google (so I don't hesitate much to use Google OAuth) but me not noticing something during casual browsing is not a very high bar to clear.
It was blatantly obvious to me within a few years that FB had no interest in thinking through the implications of data sharing. There was a time when a friend liking a picture of their friend would show up in my news feed and clicking through it would expose the entire album to me - who is not even remotely connected to that person. That's the day I went frantically removing photos of friends and coworkers from FB and eventually all of mine as well. Facebook is very unlikely to earn back my trust ever.
So about 0.1% of the American populace knew that. (Ball park: call Facebook 30k employees. If you want to add a whole lot of digital marketers take that to even as high as 3M. That's still only 1% of the US population.)
