This is cute, but doesn't really do anything which isn't already possible with EC2 and S3. The most critical limitation of EC2 and S3, at least where databases are concerned, is the "eventual consistency" model: If you store data, you'll eventually be able to get it back -- but there are no guarantees as to when.

When I heard rumours that Amazon was going to be launching a database service, I hoped that it would solve this problem; instead, it seems that Amazon has released the world's first "database" which not only transactions, but even lacks consistency!