Just curious why would someone want a spent coin? Obviously you wouldn't want to fund it since someone has private key?
Because you can handle it, it's pretty, you can show it to people, you can frame it and put it on your wall, whatever you want.
With a funded casascius coin, it's worth a multiple of the face value (2-10x often). You don't want to bring that anywhere or show anyone for fear of it getting stolen, and you don't want to touch it for fear of it getting marked. Would you wave around five (or more) $100 bills in public?
Some folks stick a new hologram on it and fund that, but I think its a waste of time because the value of these is knowing that they came from Mike Caldwell (so they can be trusted). A random dude sticking a random hologram on the back of a spent coin proves nothing to me unfortunately.
Basically, less of the value of a casascius coin than you might think is tied up in the digital part of a physical bitcoin; a lot of the value is in the novelty of it and the collect-ability of the physical coin, and a spent coin still holds some of that value. It's an accessible piece of bitcoin history.
scotjam
