kmtan: As far as I know the app doesn't work anymore.
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Looks like everything works fine again. Thanks.

I have no malicious intention, but I did some brainstorming about orderbook manipulation.

I noticed that larger buys/sells spread over a few orders take some time to get executed and actually it looks like as if those covered orders are filled one by one. Let's say I'd stuff the orderbook with a massive amount of smallish orders and a buyer/seller would initiate a buy/sell. Would it be possible to remove the later orders before they get filled after that order has been initiated or is the book locked in that moment? Would the first fill of the bait-orders be propagated through the API before all of them have been filled?
It sounds like that would require some really precision timing to work right, which I doubt is possible.
However, if you want to maximize your ability to buy through orderbook manipulation, then generating a large number of small orders is the way to go. When you have insufficient balance, BTCTC will cancel your orders up to the point where you have sufficient balance to cover them on any one specific stock. So, let's say you place an order on two stocks that have an identical price, stock A and stock B... with stock A you have 20 bid orders of 10 stocks each, and with stock B you have 2 bid orders of 100 stocks each. You make a trade on stock C which drops your available balance. On stock A, the first 2 orders are cancelled, leaving you with 18 bid orders of 10 stocks each, and on stock B your first bid order of 100 is cancelled, leaving you with a single bid order of 100 stocks. With a larger number of smaller orders, the cancellation leaves more order volume in place.