The world's 85 richest people control as much wealth as the poorest 3.5 billion. That's according to a study by the humanitarian group, Oxfam — and it's caught the attention of the movers and shakers at this week's World Economic Forum in Davos, Switzerland. With the US leading the way, the gap is growing between the rich and the rest, provoking stark warnings about social stability. We hear how income inequality got to be on the agenda for the rich and powerful at Davos. How did the very rich get that way? Will they ever share their wealth willingly, or is greed a form of addiction?