I want to run a website like stock photos. How can I be sure that the uploader is real copyright holder of the picture? Is it possible to leave the responsibility of this copyright claim to the uploader or at least the webmaster is responsible for the website content?
It generally confuses me, as for example, stock photo websites need a form signed by the model for photos showing a person's face. How they can be sure that the signature actually belongs to the model? How they stay safe from possible lawsuit in this case (e.g. if selling photos of a model with a fake signature?)