Today at the grocery story the clerk minding the self check-out terminals hooked me in before I could sneak past her to the express lane. And you know, she had trouble with the process. She couldn't get the frozen orange juice to scan (nobody can.)
From a user experience point of view, you have to be seriously wall-eyed to be able to keep track of what the register terminal wants as opposed to the payment terminal, which, unlike the example above, is easily two feet away.
Why do we think it's a good idea to abandon the social contract between the well-trained customer and the well-trained check-out clerk? My responsibility is to bring bags that stand up by themselves and to put all the cans of orange juice together on the belt. The clerk is responsible for memorizing all those mysterious produce codes and for balancing the weight evenly across my bags.
I want my check-out clerk, darn it!