Years ago I took a couple of available light general shots with my Praktica LTL in the handsome atrium of the Boston Public Library. A young woman stormed up and demanded that I give her the film I'd shot since she was in them. I guess she was, but it was a public place and she was quite distant and, I think, facing away. I refused, saying it was a public place, and she stormed off to get "security." We left. Sort of ruined a nice visit, especially since I am a Librarian.
These days I might have waited around to see what "security" would say to her and me. She was a whack job, I think. Plus I try to carry with me http://www.krages.com/phoright.htm a brief guide to photographers' rights.