> In theory, a system that let you scan products the same way checkout staff do without any weight checks or bagging area rules or other interruptions would be incredibly efficient. Especially if you could do things like scan the same product multiple times if you were buying multiple copies of it.

The supermarkets in Sweden work like this, the only thing some of they do is random checks. In some chains you do need to sign up with your ID ahead of time though so they keep track if you get caught in a random check.