In Paralelná Polis, we have a policy to only take pictures of people that want their picture taken. You shall ask and if you have a permission from all people on the photo, you are good to go.
There has been a problem with event photography. We would like to create nice pictures and making sure we get permission from all the people involved, especially if they are in the background is impractical. So we decided our event photographers have another tool down their sleeve: Automatic censorship using face detection.
Please note, that not all faces are detected and you should always manually inspect all images before publishing. This script is here only to save you some work. The photographer is always responsible for all the pictures they publish.