Having worked in manufacturing for a few year, I know that stuff gets reworked in the factory because it failed QC. This stuff usually is the best stuff leaving to door because it got caught, and fixed. Of course this is much different than a refurb though. Bottom line though either case is if it carries the full Canon backing. Like mentioned, give them a call, make sure the number is a US and new number.
As to the bad example..... yeah I guess. But I also belong to a few car collector clubs, and I can't think of one of these most anal people who when picking up a new car check all the vin numbers when picking up a brand new car. When buying a collectable, sure. But then were talking spending high 5 and 6 figures. Perhaps I am just a footloose guy, buy I never check the that the serial numbers match on my tvs, stereo equipment, appliances or what ever.... never had the thought. Usually a receipt and a warranty card has been enough. Go figure.... guess I will check more often now.