Unteresting question, could be. If you want to install a global currency, you have to crash the existing ones first. Then people would be willing to drop their existing national currencies to move to a global currency. In such a case the motivation to switch would be significantly higher if their is no direct link to government and central banks (responsible for the crash of the old currencies). I think it would be very difficult to install a global currency which is not accepted by the people. It would be much more easy if the people ask for such a global currency as an alternative to the existing national currencies. Of course the governments would need to take control of this global currency over time. If this is not possible, they would not push it. But if everything is tracked and monitored on the net, they could find a way to stay on top of things?