What makes a crowd a mob?

    If there are many people, sometimes everyone have their own opinion. That will cause some trouble. For example, when you are at Taipei 101, and you want to find a good place to watch the firework. You will push the person in front of you. If everyone does this, many people will start to fight and yell at each other, in this case, someone will get hurt.  

  Another example is "voting". Everyone want to be the president, if everyone is fighting for the only "President", the earth would be in a big mess.

  That's why we need police, president, king, or leader in order to avoid something "unfair" to happen.