The requirement is that they provide some of the information contained in the visitor's id to a police web application. At least, that's how it works here in Spain. But it doesn't mean the hotel needs to take a picture of your id, nor scan it. They just need to transcribe the required information. Yet some would not let you check-in if you refuse to let them scan your id or take pictures of it, that you never know how and for how long will be kept. Of course, you usually don't want to argue after you arrive at some place to make the check-in when the alternative is to sleep on the street.