Application Server Instead Of Web Server

I'm starting to see a small but growing group of sites forgoing web servers and going straight to the Application Server in the Java world. This has some obvious advantages:

• Less infrastructure
• Java doesn't have buffer overflows and is a bit more secure
• You can do much more interesting caching by having the web serving and app serving in the same layer

I was excited to see this blog today and just wanted to point people to it and see what thoughts are out there both pro and con on this trend.

Web Application Architecture - do I really need Apache?