UPDATE March 13, 2014 05:09 AM: All services up and running normally.
UPDATE March 13, 2014 04:28 AM: Rackspace engineers have found and addressed a server issue. That webserver is back up and handling requests but we'll keep monitoring to make sure all is OK.
One of the frontline webservers is under very heavy load and is unresponsive. Our operations folks are looking into it.