One of the things people hold most dear is their privacy.And while you can generally take pictures of any person who is in a public place, it is considered polite to ask them before publishing the picture, and you do need to obtain a legal model release before using their image to promote or sell any products.These things are an invasion of privacy, even if the person has opted not to employ curtains within their home.In general, in public places it's not illegal to take someone's photograph unless it's somewhere with an expectation of privacy, like a public restroom.This is why the paparazzi can get away with swarming famous people with cameras the minute they step out a door.However, you shouldn't take pictures that cross certain lines." Upskirt" photos are not only in poor taste, they are illegal in many places.The right to to keep what only concerns you to yourself is fundamental.If you're walking down the street and someone takes your picture, that's almost surly legal.Similarly, you should not take pictures into someone's bedroom (or any other) windows.The rest of the world has no right to know things, such as who your friends are, how much money you make and how you spend it, what you do in your free time, or who you had an argument with.That's their choice