I agree that digital currencies will play an important role in the future of finance. The problem I see with Bitcoin is of ecological nature: The strength of the blockchain is based on mathematical problems which take computers a long time to solve. Solving these problems has no intrinsic value, it only makes sure that manipulating the blockchain is extremely difficult. As a consequence, a lot of electric power is wasted on useless computations, creating a large CO2 footprint. To create a sustainable crypto-currency, it will be necessary to overcome this problem.