I think you should first and foremost show a respect for individuals and if you are taking pictures that contain people this should be done in a way that doesn’t intrude their private space. For instance, when they are just figures within the framework of your composition, but not when they are doing something that could be personal to them at that point in time, like being sick or whatever. I also think in your face photography (which I understand some people do) is totally disrespectful to the individual. Perhaps a lot of paparazzi photography falls under this verboten heading.