What would prevent a user from locking the coins after they have received the merchandise? Someone could easily use this as a way to scam legitimate sellers of their goods.
I was discussing a mechanism for altcoins where the wallet would have the built in escrow features, similar to Ethereum's built in contracts. The idea was that you trade one altcoin for another, with the transaction information included in the label. Once you ...
Of course, if you wanted to send #coins or even lend them unsecured, you could just hit the Send button or Lend button, but details are still included in the label for the transaction, leaving a paper trail that you can access if someone is merely pretending to be someone you know.
First, you never get your coins back. Although you have locked them, they are in the hands of someone else, who simply cannot spend them. At this point, it takes the owners of both wallets to recover part or all of their value, so both have an incentive to reach some mutual agreement. If the other guys turns out to be a complete scammer, I'm not letting keep even 5%. If a seller is late sending merchandise, it must contact the buyer and perform due diligence to convince the buyer to unlock some or all of the coins.
If both agree to an arbiter, then the buyer must send the transaction unlock pass phrase, while the seller (who's holding the locked coins) sends the actual locked coins to the arbiter wallet. If the proof can be a bit of text found at some url (tracking number, shipment confirmation, blockchain.info, etc), then one could even have an automated escrow/arbiter.