It will be nothing short of catastrophic if cryptocurrency were to suddenly disappear, many people have invested so much of their funds into it that they will find it hard to survive. What can cease cryptocurrency to exist will surely affect almost every areas of life especially in finance, I'm sure that everybody's bank account balances will also disappear, it will shutdown everything and life will become survival of the fittest. The physically strong will dominate and rule over everybody because money and influence will no longer control power. We are just being imaginative and wondering the worse case scenario, in reality I believe that it is next to impossible for internet to totally shutdown everywhere in the world at the same time.