This could be useful if your site has an extended outage one day. Create a bucket called "mysite.com" and another called "www.mysite.com" and put your failwhale page in it (set to be the root page). If your site goes down and you know it will be down for an extended period (ouch), you can change your domain's DNS entries to point to s3.amazonaws.com. Then at least your customers will have an explanation.