The Social Contract Theory played a large role in John Locke's contribution to the constitution of the United States. Basically, the theory states that people gave up power for the good of the order. John Locke theorized that although the people sacrifice power, they have natural rights which they cannot have taken away under any conditions. In this way, the constitution supports the social contract theory, but also limits it (setting a defense mechanism against dictatorship).
A common criticism of Social Contract Theory is that if it were the true origin of government, then people with conflicting views or rules would fight with each other. Proponents of the theory point out war. Humans often fight over territory and food, but there are also holy wars and wars of ideals.