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.