Thank you for this.
This is probably obvious to most, but it was a bit puzzling to me when I went through the text before watching the video. The beans.xml file needs to have some content, and not just be an empty file. If you add a single <beans\> element like in the video, everything is happy. If you have no elements (either completely empty or just the <?xml...> banner, the deployer will throw a org.jboss.weld.exceptions.IllegalStateException. Using a dummy element (<bob\>) will show a validation error in the log, but the servlet will still deploy and run properly.
I am using Sun JDK 1.6.0_22, Eclipse Helios SR1, JBoss Tools 3.2.0 and JBoss AS 6.0.0.20101110 CR1 with JBoss ESB 4.9.