1. SimpleDB doesn't really compete with Oracle. SimpleDB it isn't ACID, Oracle is ACID before it is anything else. Oracle has its own programming language, XML features, a very advanced SQL dialect, and many other features that SimpleDB lacks. Similarly, SimpleDB has a distributed replication feature that Oracle doesn't have.

It is interesting that Amazon uses Oracle AND Oracle BerkeleyDB. I wonder how Oracle TimesTen compares to BerkeleyDB for this use case.