Bitcoinica is not an exchange. We guarantee liquidity based on current orders in the market. If you build a fake bid wall, Bitcoinica will think it's easy to sell.

If you sell on Bitcoinica in large amounts, it's likely that the system will give you a good price since it's easy to sell. However, if you now suddenly cancel all the orders, the system will fall into a trap and make a loss.

We have already pushed some updates to refine the algorithm to prevent cheating like this. But the financial loss is not just affecting the platform itself, but other traders as well.

I don't decide who can or cannot trade. But for any transactions on Bitcoinica, I'm the counter party. I can refuse to offer prices which definitely don't reflect market conditions.

For 99.9% of Bitcoinica traders, blocking malicious accounts will benefit you.