There seem to have been multiple "full" outages in 2011-12 in AWS' us-east-1 region, which, granted, is the oldest AWS region and likely has a bunch of legacy stuff. By "full" outages I mean that a few core services fell over but the entire region become inaccessible due to those core failures.
Im forseeing a full downtime in Frankfurt this winter tho. Germany is in really bad position when it comes to electricity.