I tried to add some insight on another comment, but it's tough to say anything about DDoS that hasn't already been said. DDoS attacks suck, mitigating them requires a multi-prong approach and proactive monitoring and agressive banning and even then you can still be screwed if your bandwidth is saturated.

I feel for the operational folks at Zerigo - dealing with this type of outage is hard. The best thing they can do at this point is get back on Twitter and talk to their customers - the last post was 4 hours ago - that's a lifetime when your system is critical.