I found a quote, by Ryan Calo, an assistant professor of law at the University of Washington, who specializes in privacy issues. It's in the context of photography, and how the dynamics of it changed in the last century: You had to sit there and pose. You not only had to give your consent, you had to cooperate a lot.
The part I want to focus on is the part about your consent to be photographed. Did you really? Had to give your consent... I mean, you'd obviously be aware of the fact you're being photographed, if you payed someone to do it, and are sitting in front of a camera. But did people of the late 19th century had the same notion of privacy as we do today? I highly doubt it.
I guess most privacy laws exist because people are naturally evil. I mean, think about it. Give me a rational reason, for me to be forbidden, or it to be inappropriate, to take your picture, while you’re having lunch, at a restaurant, and I was sitting at a neighboring table? Other than the thought of possibly some nasty sexy things going on later, involving your printed image, and say my dick in my hand...