@Harrydre
Currency/money is not just a medium of exchange and I know you know that, Facebook credit, credit cards, digital currency provide the medium of exchange but quantification of it still sits right squarly on money as it is, Bitcoins is an example of medium of exchange but can you store value with Bitcoins? Of course monetary systeems have changed over time but fundamental reason for having the system has remain the same since it was first founded and that primary reason is price stability.