Two decades ago, the World Health Organization and other public agencies were the leaders in improving health in the developing world and battling the private sector on issues like infant formula and tobacco. But today, inter-governmental bodies like the WHO are being outpaced by private sector efforts led by multi-national businesses such as Coca-Cola, Exxon Mobil and drug companies like Pfizer. What's driven the change? Why have some of the corporations blamed for public health problems become leaders in the global fight against deadly disease? Are there conflicts of interest?