My dog did not have a chip. I think implanting the chip should be based on the temperament and behavior of the dog and the beliefs of the owner.
If your dog is prone to wandering or escaping his territory, I would consider it.
If you have any religious/philosophical scruples about implanting a chip, then I would not.
Microchips and Cancer Updates.. http://thewholedog.org/wholedognews/?p=593