When you use the admin console to deploy (in exploded form) an EAR that does not contain META-INF/MANIFEST.MF file, you will see an error like this>

Failed to create Resource mock-ear.ear - cause: java.io.FileNotFoundException:/home/jmartisk/builds/jboss-eap-noauth-5.1.2-ER2/jboss-as/server/default/deploy/mock-ear.ear/META-INF/MANIFEST.MF (No such file or directory)

The EAR application (at least in my case) still gets deployed properly, but this error message might cause confusion to the user.

Full stacktrace from the EAP log:
java.io.FileNotFoundException: /home/jmartisk/builds/jboss-eap-noauth-5.1.2-ER2/jboss-as/server/default/deploy/mock-ear.ear/META-INF/MANIFEST.MF (No such file or directory)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(FileOutputStream.java:194)
at java.io.FileOutputStream.<init>(FileOutputStream.java:145)
at org.rhq.plugins.jbossas5.deploy.AbstractDeployer.deploy(AbstractDeployer.java:156)
at org.rhq.plugins.jbossas5.helper.CreateChildResourceFacetDelegate.createContentBasedResource(CreateChildResourceFacetDelegate.java:124)
at org.rhq.plugins.jbossas5.helper.CreateChildResourceFacetDelegate.createResource(CreateChildResourceFacetDelegate.java:56)
at org.rhq.plugins.jbossas5.ApplicationServerComponent.createResource(ApplicationServerComponent.java:317)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.rhq.core.pc.inventory.ResourceContainer$ComponentInvocationThread.call(ResourceContainer.java:525)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)

to reproduce, you may use for example this file: http://scratch.englab.brq.redhat.com/jmartisk/mock/mock-ear.ear