I guess the question I would ask is how the dogs that are tattooed are registrated. The more modern thinking is the micro-chip which animal control has, vets have and humane societies have. They also can go into a large data base or call the companies to see if it is registered. Very few people tattoo anymore. Also if someone stole your dog then they would be on their guard because they could see the tatoo but with the chip they might be dumb enough not to realize it is in the dog. I could be wrong but I think AKC required the chip now and not tattoo's.
How do they tattoo the dog? The chip takes seconds and I cannot imagine the pain of it being done on the belly