Earlier quoted context omitted.
http://downdetector.com/status/aws-amazon-web-services looks like a reasonable alternative place to check/report downtime.
Gah. It was up 3 minutes ago. Anyone have any suspicion this is another ddos episode? I saw that SO was down last night too: https://twitter.com/StackStatus/status/836450836322516992
I'd bet that something broke (causing InternalError responses) and then nodes started marking themselves as failed (causing the timeouts and 503s soon after).