Here are a number of articles you can read. In 2005 (I believe) a bill was introduced to micro-chip all animals but it was lost because at that time their was not a universal chip. Each company had developed their own and would not realize any information to the others so it has created at least 5 different companies with 5 different readers. So if you animal is lost and the shelter finds them but doesn't have the correct reader then the information cannot be read. There is now a universal chip/scanner but to my knowledge a new bill has not been introduced. This is going on in many countries of the world and is not just a cat and dog issue. All of my animals are micro-chipped with Home Again.
I think people need to understand who can read what chips in their area. I also believe more harm has been done because of vaccinations then micro-chips at this stage of the game.
Microchip Study Microchipping of animals FAQ Microchipping of Animals AAHA Launches Universal Pet Microchip Lookup Tool | Oregon Veterinary Medical Association Microchips and Your Pet