Levels of Distractibility: Who cares? = *. Some people will be distracted from your meaning: = **. Many people will be distracted from your meaning: = ***.
Question: "He was so happy at your coming...." Benny Goodman's mother to Benny on his learning of his father's death (from the movie, The Benny Goodman Story). Why not "...you coming"?
Answer: Not many people get this problem right. The concern is with Benny's (your) coming, not Benny. If he had been concerned with Benny, the sentence would have to be rewritten: "He was concerned about you."
Another example will be the best explanation: "He was concerned about the plane's leaving." He was concerned about the "leaving," not the plane. "Plane" becomes possessive. If he were concerned about the plane, on the other hand, you would need to rewrite the sentence: "He was concerned about faulty maintenance on the plane, which was leaving." Got that?
Rating of Distraction: This is one of those judgments that rewards rather than criticizes. If you are able to determine the emphasis on "leaving" or "plane" you deserve a blue ribbon of merit.