Unless you are completely wrong, and the attack was largely contained by the safeguards built into their system. You know, the safeguards that you for some strange reason assume don't exist.
No assumptions required. The market went from around $17 to $0.01 within minutes. Where were the safeguards, or is a 99.95% drop in the market considered normal? The onus is now on Mt Gox to explain what security was present previously, how and why it was broken now, and what steps will be taken in the future to secure both the site and market. They need to explain each in detail as security through obscurity or 'trust us' doesn't work. I look forward to a full report from them once they've had a chance to fix the damage.