Most shoplifters are amateurs; however, there are people and groups who make their living from shoplifting, and they tend to be more skilled. Generally, criminal theft involves taking possession of property illegally. In the case of shoplifting, though, customers are allowed by the property owner to take physical possession of the property (holding it in their hands or in a shopping cart controlled by them, for instance). This leaves areas of ambiguity that could criminalize some people for simple mistakes (such as accidental hiding of a small item or forgetting to pay). That is one of the reasons that penalties for shoplifting are generally lower than those for general theft.