I love using the self-checkout kiosks at my supermarket. If you only have a few items they are quicker than waiting for a teller.
Apparently supermarkets overlooked something. While they have gained cost savings with these systems, there has been a 45% reduction in the sale of checkout items like candy and tabloids.
The law of unintended consequences occurs when a system is put into place with the intention of creating one result but instead produces another conflicting result.