• blog post pinning the blame on Amazon
  "Even before the serious outage last night, we suffered random disks degrading multiple times a week. While we do have protections in place to mitigate latency on a small set of disks by using raid-0 stripes, the frequency of degradation has become highly unpalatable. To Amazon's credit, they are working very closely with us to try and determine the root cause of the problem and implement a fix."

specific outages

• 2011-03-30, frequent 502 and 504 errors [1] [2]