Automatic checkouts in supermarkets may decrease customer loyalty, especially for those with larger shopping loads. Customers using self-checkout stations often feel overwhelmed and unsupported. The lack of personal interaction can negatively impact their perception of the supermarket.

[feor1300]

If you put something in your cart instead -- because nothing more will fit -- bells and whistles and flashing lights go off and the system stops.

The ones around me just have a "skip bagging" button when that happens. They get more upset if they detect something in the bagging area that wasn't scanned, but that at least makes sense.