I don't share that "binary view of sharing on the internet".
I store photos "on the internet". I also store emails in Gmail. I face-tag photos with whoever is in them, for the same reasons I tag emails with whoever they relate to.
This is as if Gmail were to automatically share my Gmail conversations whenever I mention someone in an email.
I've got a better one: You write a cheque to somebody, and suddenly your bank lets them see your transaction history.
There's a level of control and security one may sacrifice by doing things online, that doesn't mean the information is automatically public, and it definitely doesn't make it OK for Google to treat it in an entirely unexpected way that actually violates ordinary privacy/access control rules.
I store photos "on the internet". I also store emails in Gmail. I face-tag photos with whoever is in them, for the same reasons I tag emails with whoever they relate to.
This is as if Gmail were to automatically share my Gmail conversations whenever I mention someone in an email.