A politician's wet-dream is a cash-free society because every payment can be tracked, taxed, examined and stopped if necessary. It also means no bank-runs because it will be impossible to cash-out in a cash-free system.
Cash-free means that every payment is done electronically with no need for notes and coins at all. On the surface this seems like a great idea; no messing about for the right change, etc. Unfortunately there are many big problems with it :-
Privacy every payment, along with time, location and item(s) are recorded. There is a good chance that information is passed/sold to other organisations.
Reliability Anyone paying attention to the news can't help but notice that bank IT system failures seem to happen every year now. Things are getting so bad that many recommend that you always have cash available just in case.