Should we be Fungible?

Fungible, the Word of the Day for Thursday, May 19, 2011,means:
adjective: 1. (Law) Freely exchangeable for or replaceable by another of like nature or kind in the satisfaction of an obligation.2. Interchangeable.
noun:1. Something that is exchangeable or substitutable. Usually used in the plural.
Although the above was not technically referring to humans, I was wondering, first, whether or not we were in fact Fungible, and then, whether it was a good idea for us to always be fungible too?
On the one hand we need to be fungible to the point that we could be easily replaced without problems in our working lives. But on the other hand, I feel that we should also be in-fungible in other aspects of our life. Otherwise we might as well be fungible robots! Again, what say you?