This "cloud-pocalypse" simultaneously affected multiple availability zones in US-East. Had you had the misfortune to have your multi-AZ pair in two affected zones you would have had significant downtime. The only architectures that were truly safe from this outage were those with a completely multi-region strategy, and I suspect those are very far and few between.
I am still waiting for Amazon's post-mortem, which I hope is honest. All the other services (4sq, Quora, etc) seriously were all in the same AZ and made the mistake of spreading their infrastructure to multiple AZs?<p>Amazon has seemed rather dishonest about the true breadth of the outage.