I'm glad this thread keeps getting bumped, because it is reminding me to have the dogs chips checked each time I take them to the vet. Which I will do next week to get their weights and I'll have them check.

I met someone at the dog park that had to have the chip removed because it floated around. It said it was a rare occurence, but he had a new one put in.
I've also never heard of anyone I've met having them tattooed, but I think either one (or even both) are good.