I ran into an interesting situation yesterday at a local hospital. I went to visit my father who was admitted there from the emergency room. Inorder to visit him, we had to have some form of ID (they asked for DL) inorder to visit! They scanned my DL into their system and printed off a "visitor badge" with photo and all. This badge expires every 24 hours. So the next day, went to visit. They only needed my name and pulled my "visitor badge" info and printed off another badge with the current date.
I am working on my levels of privacy and haven't gotten the passport yet, and should have discussed this privacy invasion with someone there at the hospital. But just thought I'd let others know of a potential situation where you'd be asked to identify yourself and they keep copy of your ID. Maybe tomorrow I'll get into the situation with the hospital and ask them what happens if someone doesn't have ID or such, how long they keep the copy of DL, and other privacy related questions.
My wife was in the ICU of a small hospital twice this past spring and had many visitors. No one was ever asked for ID.
Perhaps larger hospitals have stricter rules.