I'm not a great fan of duplicating effort. I do find, however, that there are benefits to tracking agile iteration progress on both a physical card wall and an online "calculator" (Excel, some scrum tools) or an online card wall (e.g. Mingle).
I find that a physical card wall in the team space provides a visceral kind of connection to the status of the cards... and that moving a card physically when you finish something provides a level of satisfaction that can't be duplicated online. I can feel the card... and people can see me walk up to the wall to move something.
Online tools provide great capabilities to share remotely and to calculate progress (e.g. in Mingle, you can use the built-in tools to automatically calculate burn-ups or burn-downs from the real data, saving lots of administrative time in doing those things manually).
I'm curious if agile practitioners maintain two tracking media like I do, and how do you present the benefits of the physical wall to those who say "I can do it online... why would I want to do it on a card wall instead?".