I understand a British property owner in Calis has been served with a 20,000TL fine for renting out to holidaymakers without registering the property.
More importantly possibly, the renters were allowed to stay, but only because they could show they only had a few days of their holiday left -
by showing their return flight booking details. The police confirmed that had it been at the beginning of the holiday, they would have been evicted.
So those who believe nothing will happen to them if they don't register, need to rethink. And people who innocently book a private apartment/villa need to see evidence it is registered or they could find themselves out on the street.