I'm surprised amazon hasn't built another region in the east. If you're in the west you get US-West-1 and US-West-2 and can failover and distribute between the two, why don't they have that kind of duplication in the east?
us-east-1 was 11 different datacenters last time I bothered to check.
us-west-2 by comparison is two datacenters. The reason west-1 and west-2 exist is because they are geographically diverse enough to prevent low latency inner-connections (and also have dramatically different power costs so they bill differently).
then how come when east goes down, it always seems to take down all the AZs in the region, never just one AZ? As long as the region fails like a single datacenter, i'll think of it like a single datacenter.
They already expanded into a DC in Chantilly, one more in Ashburn and I believe one in Manassas. But they lean on Ashburn for everything they do, and a small problem results in a daisy-chain failure (which because everyone uses Amazon for every service imaginable, means even the smallest problem takes down whole websites)