The Tarsnap website went offline at 1:05 PDT and attempts to launch a new instance in the same availability zone have failed. I'm also seeing the EC2 Management Console getting very slow -- possibly because lots of other people are logging in to investigate their failing systems.
As of 1:40 PDT I'm seeing EBS requests served and the Tarsnap website is back online.
Amazon's status page reports:
1:22 PM PDT We are investigating degraded performance for some volumes in a single AZ in the US-EAST-1 Region
1:29 PM PDT We are investigating degraded performance for some EBS volumes and elevated EBS-related API and EBS-backed instance launch errors in a single AZ in the US-EAST-1 Region.
RDS and ELB are also now (1:40 PM PDT) showing "investigating connectivity issues". Sounds like there was a core networking outage in that AZ.
2:21 PM PDT We have identified and fixed the root cause of the performance issue. EBS backed instance launches are now operating normally. Most previously impacted volumes are now operating normally and we will continue to work on instances and volumes that are still experiencing degraded performance.
If they have managed to keep this incident confined to one AZ without trashing the whole region they have made significant progress.