One think that I think may be oversubscribed at EC2 is the API layer for controlling things like instances, ELB's and autoscaling. This seems to be most obvious

One think that I think may be oversubscribed at EC2 is the API layer for controlling things like instances, ELB's and autoscaling. This seems to be most obvious in Virginia. During the lightning storm in Virginia last summer, it seemed like API access fell off a cliff. I'm guessing that was because everyone was trying to move their services from the impacted availability zone.