Thanks!
Or maybe you want to buy a rare Magic the Gathering card, but don't trust the Online eXchange. You find someone who will sell the card for 200 BlackCoins, but neither of you are comfortable sending to the other person first in case it's a scam.
You create a BlackHalo contract and both deposit 300 BlackCoins each - you each hold one of the keys to this money. They send your card to your safe deposit box, you send the BlackCoins to their address, and once you're both satisfied that everything is fine, you sign the contract transaction and both parties receive their 300 BC deposit back.
If I'm buying the Magic the Gathering card, and receive the card, but claim that I didn't, the following happens:
I will get the card (+200), but lose the deposit (-300) => total -100
The seller will lose the card (-200) and lose the deposit (-300) => total -500
Is this correct? What will happen to the deposits (total of 600) ? No one else knows that I have actually received the card even though I'm saying I haven't.
Yes, that is correct. If the buyer/seller never reach agreement, no one will get their money back. The coins would essentially be destroyed. (At least for this simple contract.)
You could structure the agreement differently, for example, the seller of the card deposits 100, the buyer deposits 300, and once the contract is completed, it will send 300 BC to the seller and 100 BC to the buyer. Once the contract is setup, the seller sends the card and signs the contract transaction (he has no reason not to.) Once the card is received, the buyer also signs the transaction, and the payment will be received. (There's no way to keep the total value at risk always equal between the two parties, because this changes as soon as the card is sent.)
I just chose the larger numbers to illustrate that the cost of breaking the contract should be greater than not doing so. Because the BlackCoin market is currently somewhat volatile, the higher amount reduces the chance of a backout due to market price falling. You'll be able to choose whatever escrow amounts are desired to balance ensuring you won't get scammed vs not placing more than needed into the escrow address. (And some types of transactions can be broken into multiple steps to further minimize the escrow requirement.)
I think there are many reasons for low prices - BTC just had a major shakedown which in turn tanked almost every alt, fickle traders just trying to get in on the 'newest' pump and dump (today Mintpal ninja launched Cloak just as we were rising...people dumped BC and started pumping Cloak), daytraders that bought in when BC dropped to the teens are cashing out because they are happy with their profits, and on and on. It'll rise soon enough - this coin is resilient and has too much support and innovation to ever fail. Even after that artificial pump, it never fell below where it started. Remember it was trading at 500-1000 sats earlier this year. People will realize the fundamentals of blackcoin are solid - not like any of the clone coins or p&d coins or scam coins...we are here to stay. 
