In brief: Farmville is popular because in entangles users in a web of social obligations. People are built to be social and be entangled in social obligations

In brief: Farmville is popular because in entangles users in a web of social obligations. People are built to be social and be entangled in social obligations with other people. This may be less reflected in modern life than before but the tendency to get involved in that is nothing but gone. Earlier, these social obligations had a big role in reducing risk of famine and ensuring the continuum of life by making people do things together and keeping them doing that.