The method looks intriguing to be sure.
My quick read is that the goal is to redefine your approach to email in two ways: how you process it and how often you process it. I am almost reminded of the getting things done approach, only applied to email.
I don’t think that implementing the stack method means that you cannot have well-developed folder structures to archive email for historical records. It simply means that you also have a parallel approach to treat email as actionable items, and that you do so in a well-defined way (the stack method rather than the GTD method).
Thanks for the link. It gives me some support to know that I can likely be more productive when I purposely shut down the buzz that I get around email. I may start to template some of their approaches into my own email processing routines.