I heard about this at a talk over the weekend and it sounded like a great idea for a few reasons I can think of:
- ensures dependencies are met and not broken (e.g. web app requires specific version of imagemagick)
- helps make spinning up new servers fast
- consistency with os packages and ease of deployment
- (potentially) keeping configs updated with the code so that changes to apache, php, etc. configs are kept current with code dependencies. I can see this is a gray area since it's getting into config management.