Time magazine (November 14, 2011) has a good article on social mobility in society. They site education, technology, health care, and the market as some of the factors playing important roles.
"A large body of academic research shows that inequality and lack of social mobility hurt not just those at the bottom, they hurt everyone. Unequal societies have lower levels of trust, higher levels of anxiety and more illness. They have arguably less stable economies: International Monetary Fund research shows that countries like the U.S. and the U.K. are more prone to boom-and-bust cycles. And they are ultimately at risk for social instability."