Sido, your very very very mistaken here. What happened i think on DMM that time was that a broker type'd in the wrong quantity on the order and so he instead of buying 'some' he bought 'plenty' at market and wiped out the entire depth.
This happens regularly. The offending broker can contact the brokers and clearinghouse who was on the receiving end of the trade and they can have the false or accidental order cancelled.
Its a regular occurance