This is a good principle in general but you didn't exactly put those words up on a site that promised "privacy/protection" did you? That's the difference here.
There was absolutely no way these companies were not going to exploit the crap out of both their position and data.
None.
How were they all built? As fast as possible, growth first, etc... I expect these kinds of things to boil down to risks and costs, ideally paid after the enterprise is big enough to deal.
And a whole lot of us know it too. How else was it all going to go?
I am a realist. There is no real privacy online. One can get close, but doing that is a lot of work, takes understanding, and is still a bit of a risk.
Long ago I realized it is better to just not put things I can't live with online.
Frankly, I won't do that electronically, unless it is very worth it.
Edit: It is all still pretty new. We are leaving the honeymoon time. Bad things will happen, so will more regulation, and that crank will get turned a few times.
My expectations are super low right now. That could change, but not yet.
I pretty much don't put anything online I cannot live with.