I agree in principle with you, Bynx. I also agree with Dave. As a US citizen, I can expect privacy in my own home, with the blinds drawn. Almost everywhere else, I am fair game. Recently in my town a man was brought to court for an "upskirt" view he took at a local bookstore chain. He was basically let go, because the law was too vague. Naturally, the young lady was upset, but to no avail. It was determined that, although he acted like a jerk, she had no reasonable expectation of privacy in a bookstore, which is a public place.
I agree that it would depend on the usage of the photo as to whether it "violated" someone's right to privacy. I have shot candids at local events, like our annual "mullet toss", where people are drinking and acting somewhat foolish. Being on the beach, the photo ops are fantastic. What I do with those photos, as opposed to my right to take them, is a horse of a different color. If I snap a young bikini-clad girl who is tipsy and having a "wardrobe malfunction", I feel a moral obligation to keep that shot private, and not post it on the web anywhere. I would expect no less in return.
Common sense should come into play as well. Never shoot pics of small children unless you are related to them or they are with parents who are okay with it.
There will always be a debate on this subiect, and I always use the Golden Rule, which applies to almost everything. Treat others the way you would have them treat YOU..