I guess we have been lucky. We have seen some of these things happen at other parks, but never at WDW. We have been twice, one 11 day trip and one 9 day trip. The only shocking thing that we saw happen actually happened to us and involved a CM.
My DD has had a history of complicated medical problems, and to make a long story short, at the time of our first trip to WDW had difficulties which included weakness and fatigue of the muscles in her arms and legs. She could walk fine, but tired quickly. I rented a stroller for her. Thanks to these boards, I knew that if we wanted a good spot for Spectro Magic we would have to find a spot early. We grabbed snacks and picked a spot along Main Street a full hour before the parade. I pushed DD's stroller right up to the edge of the curb, behind the rope. As the parade time approached, it became quite crowded. We were a feet from one of the places where there was a gap in the rope to allow people to cross the street and get up on the curb. Poeple began blocking this cross. CMs kept coming over and asking them to clear the walk way that it had to remain open, and the people would leave, only to return when the CMs walked away. One lady and her two children did this several times and were very rude about it. Just as the parade started the woman and two children came again, a CM came over and told them that they had to step to the side and pushed them right in front of me, my DD, my DM and DDad. I actually feel backwards and a man behind me caught me. I looked at the CM and said, we have been standing here for an hour to make sure that my DD had no one in front of her. She said, "I can't help it. Your daughter should be standing if she can't see." I said, "She was able to see until you put them in front of us and she can't stand through the entire parade." The CM interrupted me and said, "She looks perfectly capable of standing to me" and walked off. My DD cried the whole time saying she couldn't see anything. To make it worse the woman who was put in front of us made sure that she put her head, arm or something in every picture that I took. She made sure that I knew she was doing it on purpose to.
Other than this one incident, we have experienced nothing but true magic at WDW.