Refurbs come from several sources. They could be returns that can no longer be sold as new. They could be items that were returned to the dealer within the dealer's return period; this could be that the buyer changed their mind or there was a problem (either real or perceived). When returned by the dealer, Nikon sends them to their service department for a thorough check. If a problem is found, it's fixed and sold as refurbed. If it checks out ok, it's sold as a refurb. Another possibility, one that I experienced personally, was replacement for an item sent for repair. I had a lens that fell and I sent in for repair. They repaired it (I paid) but it had problems during the repair warranty. Just as I sent it in, the tsunami hit Japan and parts were not readily obtainable. They sent me a refurb instead. Sadly the refurb looked like it had been thru a war and I insisted on a suitable replacement which they did send. I suspect when parts arrived, my original lens was repaired and used as a refurb for someone else or sold as such.
Refurb bodies have been seen with near zero clicks or with 10,000+. Nikon typically doesn't discount their refurbs enough for me to take the risk of getting someone else's intermittent problems that got past their checks. When Nikon decides to blow out some refurbs to a dealer like Adorama the deals seem better but in my mind, there is nothing like a 5 year warranty on a new lens. With the amount of electronics in them, it's no longer a matter of if something will fail, it's when.
