My wife often plays this role. At that time, my wife will warn the riders about me as well. Obstacles are good places for photographs, and I frequently follow the judges in order to photograph a rider working his horse through such a hurdle. The resultant effort often produces noteworthy photographs. The riders appreciate these both as pictures and as records, because they provide visual re-enforcement for a judge's comments at the end of a ride.
Obstacles are also where the most wrecks occur.
At first I didn't photograph these. I thought no one would buy them, and I didn't want to embarrass anyone. But I found people actually requested them. They wanted visual proof to show their friends what they had survived. The dramatic value of pictoral proof was driven home to me after I experienced such a crash myself.