<blockquote>As I write this Friday morning, the downtime is continuing as Amazon engineers fight to fix things. The outage was caused by misconfigured mirroring services that filled up all available storage. More information can be found at the EC2 status page</blockquote>
via <a href="http://www.pcworld.com/businesscenter/article/226033/thanks_amazon_the_cloud_crash_reveals_your_importance.html">Thanks, Amazon: The Cloud Crash Reveals Your Importance - PCWorld Business Center</a>.

More info.  Who'da thunk Amazon was so into cloud services.