Video - Bitcoin Q and A Who Determines the Value of Bitcoins
Everyone, through market forces of supply and demand in international liquid markets that operate around-the-clock. A fundamental difference between bitcoin and the USD/GBP/Euro etc. is that trading never ceases; it has been continuous for 7 years. The volatility can be a roller coaster, yet if you look at the long-term trend, volume and transactions go up while volatility keeps dropping. For Argentinians and Brazilians, the price of bitcoin is not too volatile and you don't need to sell it to them, because they already understand the separation between state and money is a good idea. Volatility is relative.