I read this today and it reminded me of a conversation I had in Saga with Matt G. about sunk costs. I don't remember what either of us said, but this is pretty neat:
http://www.marginalrevolution.com/marginalrevolution/2004/03/when_is_it_rati.html
http://www.marginalrevolution.com/marginalrevolution/2004/03/when_is_it_rati.html
