Think of it this way: it's hell of a lot less painful to recover from a couple of dead (unmanaged?) switches than it is to recover from complete failure of all drive arrays and motherboards. A nice unrestrained surge through the power lines could do just that, and then a slow site would be the least of your problems. If simply powering the servers up and replacing few switches brings most of the sites back online, that's a graceful recovery from a complete power failure of this magnitude. It ain't pretty in the big picture, but given the circumstances it's not bad.
Even professionals are human. Lapses happen, and you shouldn't go waving your arms and shouting "Armageddon!" if you lose one email. That's juvenile, and definitely not professional. Look for a pattern before you pass judgment. If you see a pattern, be a professional and do the professional thing and make your backup provider your primary provider.
In this instance DH supposedly had plenty of backup power capacity standing by, but it didn't make itself available. There's been an error in judgment, i.e. relying on someone else without doing checks yourself, and a professional will learn from it. I suggest you wait until you see how Dreamhost responds before nailing them to the wall. If they fail to follow through in a professional manner... rip them a new one
Edit: did you notice what a bunch of us wrote in the off-topic section? I'm not happy with DH's level of preparedness, in case you're wondering, but I am waiting 'til I see how they respond.