So when the smart contracts are created on the blockchain between buyer and seller, a decentralised escrow is set up between the two of them. This makes scamming infeasible and ensures the buyers and sellers cooperate.

Buyer makes payment for item plus a deposit into escrow (blockchain smart contract). The seller puts the same amount of deposit into escrow (the same blockchain smart contract). Seller ships item. If the buyer is happy with what they received, they release the escrow and the buyer gets back their deposit, the seller their deposit plus payment. If the buyer is not happy then they talk with the seller to try and resolve their issue. Only the seller can release the escrow. An escrow contact has no expiration period to give the buyer and seller time to resolve any disputes. The current escrow for the beta launch is 100% of the item price; in future this will be adjustable between 100-0%. See diagram for more datils.

    

So taking a look at an item on the marketplace:

   

    The buyer would deposit 125 PART payment + 125 PART deposit, the seller deposits 125 PART and post the item. When the item arrives and the seller is happy, they release funds and receive their 125 PART back, the buyer gets 125 PART payment + their 125 PART deposit. Else they have to talk to each other to resolve any issues. This is called Mutually Assured Destitution Escrow or MAD escrow.

    Later versions of the marketplace will allow adjustable escrow deposits between 100-0%.

    I really like the design because it's exactly what stash was working on back in 2009, but he hadn't yet worked out MAD escrow, and he didn't have ring signatures, blinding and SMSG (a bit message variant developed by the Particl team for securely storing heavy data in parallel with the blockchain).