A big thing I always notice is when one person gets in line and holds it for 6 or more other people. Rather than telling that one person to come back with them, they have to cut across several others. I know that Disney does have a rule about that, but I wish it was more enforced.
The thing about the monorail I think the CMs is in part to blame. The CMs operating the monorail stations should realize if the monorail is full, then there is no need to let more in. Case in point: During our trip this December (I forget which day), the monorail was full to capacity leaving MK (This was during the early afternoon). When we stopped at Contemporary, there was a long line waiting there for people to get on. They kept putting people on, but only half of them could get on the monorail. The driver had to announce people to move to the other side to let more in. After waiting for 5 minutes, they came to realize they couldn't fit anymore on the train. While there were no fights that I noticed, this could be a possible instigator of a guest's frustration that could break out into something worse.