once is a mistake or someone really hit a good shot. as long as they yell fore, or at least apologize then I'm good. 2x or more isn't an accident. I'd take the flag out when I finish the hole and place it off to the side of the green. that should be a message when they don't know where to aim. I haven't done this yet, but saw someone else mention it somewhere before and thought it was great. When I was young kid just learning to golf at a local crappy course that had a short par 4. It was the second hole and we were walking to the 1st green. We heard someone yell four to the group on the green of #2, the tee shot came down and hit an older guy straight in the head. He dropped to the ground like a wet fish, had to call an ambulance and rush him away.