I had a close one a few years back. I was sat in a Chippy waiting to tow the next glider, before starting shouted 'clear prop' at which point a couple of people shouted 'stop!' and quickly dragged a dog away that had decided to sit in front of the prop in my blind spot - it could have been a child. Anyone who fails to ensure its clear or issue a warning before starting is in my opinion acting dangerously.