Seeing people smile or laughing in dream is considered bad as per those who believe in dream interpretation. In Hindu religion there is an ancient scripture known as Swapna Shastra which gives interpretation and meaning of various dreams.
The main belief is that those who see people, friends or relatives laughing in dreams will face mental trouble. There might be lack of peace. Sometimes it means there will be lack of interest or lethargy in life. You might regret decisions made.
Please note that one should not give too much importance to such things.
Majority of the dreams have no meaning as they are just extension of important events that took place on a day. People see mainly dreams related to matters that touched them during the course of a day.