The offending application is an EAR with 2 WARs (one uses JSF, one doesn't). It can be found in https://gist.github.com/1380689. Each WAR contains a listener which upon start performs a lookup to java:jboss/datasources/ExampleDS.
Scenario to reproduce: build application, deploy in running instance. Most of the time the first deployment succeeds. Upon a subsequent deployment, the application fails with a naming lookup error on the datasource in the JSF jar. The cause is that the NamespaceContextSelector doesn't have the jboss namespace setup (none of them, actually).