This seems easy to outsmart or confuse.
What if I go with someone that doesn't have an Amazon Go account grabs some stuff for me and throw it to me?
Or how about I go with someone that has an Amazon Go account too and we divide in two, he goes for the milks I go for the cereals. We meet just before the "check-out" and he gives me my milk I give him his cereal.
I'd need to know more about the technical stuff to know how it could be confused, or to know if it's even possible to.