Jim Harrison points out an interesting blog post by someone at Yahoo regarding what might be considered "accidental caching". What I especially liked about this article is that the writer points out that the ISA firewall isn't a "bad citizen" and in fact, remains true to agreed upon standards for HTTP. That's a common threat with the ISA firewall -- the dev team has always worked hard to stay with agreed upon standards and not make new ones on their own.
Check out this article at http://www.mnot.net/blog/2009/02/24/unintended_caching
Thomas W Shinder, M.D., MCSE
Sr. Consultant / Technical Writer