What appears to have happened is someone in our team made a gratuitous change to one of our build.xml files. The change affected what XML deployment descriptors get placed in each bean's JAR file. The missing piece was that the jbosscmp-jdbc.xml file wasn't getting included in any JAR files anymore.
We hadn't seen this behavior before since we've been using XDoclet for all of our boiler plate stuff and we've had an Oracle datasource defined from the beginning of our project. Since we weren't providing the appropriate mappings to the DB tables the bean container took it upon itself and generated tables named after our entity beans.
I guess we might have discovered this problem sooner but it looks like the principal we're using for our OracleDbRealm in the login-config.xml file has the ability to create tables. I'm thinking for security reasons we probably do not want our Oracle principal having the ability to create tables from JBoss.