Old question now, but if anyone else comes across this through a search as I did, it appears that IE9 will be making use of this to configure the behaviour of resources when using the back and forward buttons. When max-age=0 is used, the browser will use the last version when viewing a resource on a back/forward press. If no-cache is used, the resource will be refetched.
Further details about IE9 caching can be seen on this msdn caching blog post.