I've been trying to install an Oracle AMI on EC2 (using the Oracle provided AMIs). However, every time I go through and use the defaults and the installation gets stuck at 87%. It does not finish. This has happened with AMIs for multiple releases of Enterprise Linux and Oracle Database.
I was able to install and access the latest Oracle BPM AMI (http://aws.amazon.com/amis/Oracle/4052) in order to test it, but no such luck with a DB AMI (such as http://aws.amazon.com/amis/Oracle/3647).