Real world commodity exchange is possible. But escrow involves the buyer transferring funds to escrow, and the escrow account confirming to the seller that funds have hit the escrow account. From this point, the buyer and seller can communicate with each other and discuss where to ship the item to. When the item is received by the buyer, the escrow will release funds to the seller.
On a side note... I believe peer to peer exchange is a wonderful notion. But the downside is trying to find liquidity (whether its currency or commodity) in a decentralized structure. Centralization is a great mechanism for bringing buyers and sellers to a central location and this has what made centralized markets effective and efficient. Think about going back to the bartering days.
Who wants to start a Craigslist like website for the crypto-currency market? Buyers and Sellers can come together looking for (___________) and they can contact each other through NXT messaging and set up the transaction p2p. It is a great way to find goods and services in a decentralized structure.
What do you guys think?