I hear that they are supposed to have licenses that they display when they are guiding you. How big a deal is this?

I recently toured Ephesus and we had a licensed guide. All guides there (and there were heaps of them) displayed their IDs. They were also checked there by officials as the photo on our guides ID was old, and he was questioned about it.
It also means they do not have to pay entry fees at some locations.
I have been told by a friend (that is a tour leader on Turkish tours) that if you run a tour group in Turkey you must also have a licensed Turkish guide.