The deal is not anonymous and will performed as follows:
1. Buyer wants to buy goods for $50,000 paying with bitcoins. BTC/USD rate will be determined at the moment of every transaction.
2. Seller requires 10% prepayment to reserve the item. Prepayment to be done with bitcoin.
3. After seller receives prepayment, he orders the goods from his supplier (will take up to 10 days).
4. When goods is ready for the transfer of property rights, buyer transfers the remainder of USD amount in BTC.
If deal cannot be completed, seller refunds the amount of bitcoins equaled to the amount in USD/BTC rate on the moment of prepayment. (ie. at the moment of prepayment BTC=$100, buyer transfers $5000 in 50BTC ($5000/100), at the moment of refund BTC=$200, seller refunds 25BTC ($5000/200) )
Yes its tricky - It seems a reputable escrow broker is the safest right now. Once can execute a contract that leaves a legal recourse for a breach of said contract.
I am interested in the new Ripple service and how that might work with its trusted brokers etc