They save lives... but only if the animal is scanned. That is the downside, if someone finds your cat and never takes it to the vet... nothing happens. If someone keeps your cat for a year or two, and takes it to the vet and never mentions it being found, odds are it won't be scanned.
Anywho a cat in california got lost, the humane society didn't scan it, it got adopted out. The owners moved to Oregon, and now a year later they gave the cat to Oregon Humane Society, they scanned the cat and it was reunited with its real owner. So... it's good and bad. My kitty has a chip, even though I decided not to let him be indoor outdoor lol. He has it either way.
I was wondering yesterday randomly if the people who pick up bodies on the road, like dogs and cats if they scan them before sending them to county... to let owners know what happened?