There was a recent thread talking about having ID on pets. People finding dogs sometimes remove a collar and will just keep a dog. There's more out there than you think. I've seen it many, many tim...
This story was on our local news last year and is the only negative result I've heard of on the subject. Seems like application error, rather than product fault.
California people are largely VERY fond of animals and a fund was created to have a vet neurologist remove the chip. The last I heard, the little guy had been adopted as a special needs pet.