I understand it's really crowded in big cities like Beijing, but when we ususally walk, when someone's coming, people should move aside/make a room for each other, and that's pretty normal in most of countries I've been.
However, too many local people here (esp. middle age) don't know how to step aside for each other. and it seems that bumping each other's shoulder is too common that they are all used to it , and even they are immune about it. so when there is even not crowded situation, people don't move aside.
my american professor who was in china for many years since he was young (20 years ago?) told me that when he came to china and experienced crowds of bicycles, local people told him if he wanna pass the road when the bunch of bikes are passing, just look straight and don't look at bikes, walk straight and the bikes would move aside for him.
I'm not really talking about bike but i think its similar here, when local people are walking, they just don't pay attention on the front, looking at somewhere else or they suddenly stop, and exc. and it can drive foreigners nuts.