http://blogs.adobe.com/livecycle/2009/12/running_livecycle_on_amazon_ec.html
One of the major annoyances with Amazon’s Elastic Compute Cloud (EC2) has been its behavior when you shut down one of the instances. All changes you made were immediately and irretrievably lost. You had to be a programmer to backup your changes to Amazon’s Simple Storage Service (S3). If you decided to keep your instance running overnight so that you could continue working the next day, you incurred hefty charges for the 8-12 hours of night time during which you do not even use it.
Amazon then introduced the Elastic Block Store (EBS) service which essentially is your own hard disk where you could save things that would survive a machine shutdown. However, up until a week ago, you could not boot from your EBS volume. Now you can.