I just had a really eye-opening experience in regards to my dog's microchip. I recently moved, and I called HomeAgain (the company who made my dog's microchip) to update my address.
They told me that the microchip # my dog has had not been registered! I know I gave them the correct # because I recently had my vet scan her microchip for the number.
I've had her for 2 years, confident that if she got out, her microchip would mean she'd get back to me. But unless I checked into this, that would not have been the case. All this time, her microchip's contact info linked to the breeder, in another state.
When I got her from the breeder, I filled out paperwork activating and paying for her microchip with the AKC and HomeAgain- I'm looking at a copy of my enrollment form and her registration tag right now. So apparently, something got lost between the AKC and HomeAgain, or HomeAgain has crappy record keeping. I'm pretty ticked at the situation.
Anyway, I just wanted to post this for the fellow GR dog owners. Your dog may be microchipped, but mistakes do happen, even with the AKC. Also, I know so many places offer 'free microchipping' and that's true, but you've still got to activate the chip, and mail in your contact info, and pay for it in order to have the chip tied to your residence. Otherwise the chip is linked only to the breeder or pet store.
It would be a good idea to check up on your dog's microchip registration directly with the microchip manufactuer, just to make sure it is your address that is on file, and not the breeders, or the pet store's.
One last point: it would also be a good idea to have your vet scan your dog's microchip from time to time, because they have been known to stop working, etc. My vet was happy to do this for me free of charge.
I also found this page interesting, because apparently if you had a microchip put in around 2003, there are problems with them: Microchips: Common Questions | The Humane Society of the United States