I like the quote by Merlin Mann and reference by Shawn Blanc because I think it is an important perspective to keep in mind that all the inputs we process should be associated with helping us to produce outputs however indirectly. Focussing on outputs gives meaning and purpose to why we should bother to selectively pay attention to the inputs that continually bombard us.
Put to best use, Inbox Zero is merely a philosophical practice of learning to be parsimonious about which and how many inputs we allow into into our lives—and, then, to responsibly but mindfully tend to those inputs in a way that is never allowed to hinder our personal commitment to doing the work that really matters to us.
To paraphrase Robert Louis Stevenson: Inboxes are good enough in their own right, but they are a mighty bloodless substitute for work.
(Via Shawn Blanc)