I've had interactions both ways with people on the course.
I've called a stance violation on a guy who was standing in an OB area when he threw. He got a little upset and asked "why didn't you warn him before I threw?" All I could say "Ah crap, man, I'm sorry. I didn't think you were actually going to throw. I thought you were just swinging your arms around."
I've preemptively warned people and the reactions have gone both ways. "Holy crap, thanks, I totally forgot there's a mando there" as well as "Uhh, duh, how stupid do you think I am?"
I've called a stance violation on a guy who was standing in an OB area when he threw. He got a little upset and asked "why didn't you warn him before I threw?" All I could say "Ah crap, man, I'm sorry. I didn't think you were actually going to throw. I thought you were just swinging your arms around."
I've preemptively warned people and the reactions have gone both ways. "Holy crap, thanks, I totally forgot there's a mando there" as well as "Uhh, duh, how stupid do you think I am?"