Quoted from girloveswaffles:
Sorry, but you got that one backwards. When the Cash register goes down, Cash is pretty much the only option. You can't use a Smart Phone or Credit card (weather a magnetic strip or chip) if the register isn't working.
Maybe, but since the guy or gal working the register usually can't count change, then we are sometimes in the same boat as those that need their smart phones to run their lives.