There's a few articles floating around that say shoplifting is greater at self checkouts[1], but apparently its not enough to keep these jobs around without regulatory distortion.
One way of thinking about it is that the store shifts responsibility to both the shopper and the police (in the case of shoplifting) but the police might not agree to the additional workload [2]
The price of goods is a function of all of the costs associated with selling, so I think the cost in additional theft is ultimately put on the honest customers. That may not be such a terrible result though, since self checkout reduces cost in the first place. Since many customers prefer to save time / avoid human interaction by self checkout, it's probably a net gain either way you cut it.
>>additional theft is ultimately put on the honest customers.
That's true up until a certain point, but eventually the business is no longer profitable. I think this explains many 'food deserts' in low income areas