We are pretty strict about social media. Our older children are 11 and 13. They are not allowed to be on FB until they are 16. They will friend me, we will read the websites they go to, etc. At this point we have a verbal discussion about where they go on the Internet: "Mom, can I go on DIsney.com to play games?" or "Mom, I need to research echidnas for my science class. Can I do a Google search?"
We consider online stuff to be public. They will be taught it is public. Internet and computer use is a privilege, not a right. We do not listen in on their phone conversations, we knock before we go in their rooms, we don't read their personal writings, we don't go through their drawers. Internet is something else. Our kids do not have phones and text. They will be allowed those privileges as they get older. We have an extra family phone they are allowed to use if they go somewhere without parents and want to be able to contact us.
My parents gave us lots of privacy, even in a family with 9 kids. BUT there was only 1 phone in the main area, and we shared rooms, etc. If we wanted to be alone, we were allowed to go for a walk out across the sagebrush. Not much there but jackalopes.