For whatever reason, it always seems to be the company’s data center in Virginia which causes problems. (Previously on GeekWire from April 2011: Massive failure at Amazon Web Services causes havoc for Quora, Foursquare and others)
UPDATE 10/23/2012: It took almost a full day, but Amazon says it has restored most of the service at its data center in Virginia:
The remainder of the affected ELB load balancers have been recovered and the service is operating normally.
We have restored IO for the majority of EBS volumes. A small number of volumes will require customer action to restore IO. We are in the process of contacting these customers directly with instructions on how to return their volumes to service.
Volumes affected during this event are continuing to re-mirror (which we expect will continue through the remainder of the day). While this process continues, customers may notice increased volume IO latency.