An official comment:
With the situation at Mt.Gox, we are unable to manage risks in full as the spot price is basically unknown. Margin requirements were temporary increased, so withdrawal requests which would normally be processed are pending now (because otherwise they may not be able to sustain payout requirements of a BTC/USD-4.13 contract due to settle in a couple of days).
We have to care about both sides of the market, and will gladly reduce margin requirements as soon as the market stabilizes (at least opens).
How can you temporarily increase the margin call? I do not understand how you can decide to change the agreement without us also agreeing to the change? We willing put so much up for risk, and yet you are deciding we are forced to risk more than we agreed upon when we first purchased the futures contract. This isn't how you conduct business.
This exchange has a track record of arbitrarily changing the rules as it sees fit. They are not contracts in the eyes of this exchange, but just words written on a webpage that they can disregard as they see fit.
They are also manipulating trade ranges essentially devaluing the market as they see fit instead of allowing people to sell down to what they deem as its valuation. Just today they manually adjusted the price down $130, without allowing for selling on the way down. Locking the price closer to spot without allowing trades in between is not just unfair, its outright theft. It is in direct breech of contract which states the maximum move per trading session is 10%.
Just this week they agreed not to do manual clearing, instead relying on more frequent scheduled clearing, which they have disregarded as well. Having a trading session of only 6 minutes, this is a new low even for them.