Two of the main social influences on the creation of Facebook have been geographic mobility and the increasing busyness of our lives.
Americans today are very mobile people. We do not tend to live in the same town where we grew up. For this reason, we tend to lose touch with a lot of people that we knew as kids or that we went to college with. This helps to make Facebook as popular as it is. It gives us a good way to keep in touch with people who no longer live near us.
Americans today are also very busy. In the past, they might have written letters to people they once knew. But today, they do not have time for that sort of thing. Because of this, the quick interactions that are possible on Facebook are more valuable for Americans today.
It was social influences like these that led to the need for something like Facebook and which, therefore, helped to inspire its creation and growth.