Imagen a situation. I bought some tangible product. The product was delivered and I decided to deceive you and said that the product was not delivered. How are you going to deal with that kind of frauds? You need a service to monitor the shipment of the goods, I guess.
There will be a 3-rd party handling the dispute resolution legally and partially between parties. But considering that the deals will be concluded through the smart contracts there is very little % of this situation to happen. However we will be prepared in case it does.