The scanner that Congress wants to bring in is the one used in Europe, which is on a much higher frequency than the ones used in the United States. There are two different scanners used in the United States that do not always read each other's chips. They are also having problems with chip failures, which is why about a month ago, the United States Veterinary Association recommended to stop chipping animals for the time being and recommended tattooing.
http://www.avma.org/onlnews/javma/jul04/040701a.aspThis was the first reported case, but there have been others since and there have doubtless been many unreported cases. Also, although new chips aren't supposed to "migrate" or move around under the skin, this is still a possibility. There is absolutely no way for a chip to form a bond with soft tissue, despite claims of "adherence."
Also, a quote from the Colorado Veterinary Association website:
What is the problem for veterinary hospitals, animal shelters, and humane societies with different types of microchips available on the market?
Each company that manufactures microchips also manufactures scanners to read their microchips. In some instances, one manufacturer’s scanner may not be able to detect the microchip of another manufacturer. This could lead animal care professionals to assume the lost animal is not microchipped.
Without the ability to use a scanner that can detect all types of microchips, veterinary and sheltering professionals would have to scan the animal, which may be fearful and difficult to handle, multiple times with each manufacturer's scanner. This is not a feasible option given limited staff resources.
http://www.colovma.com/displaycommon.cfm?an=1&subarticlenbr=98After the American Veterinary Association Convention this year, a statement was issued recommending that people tattoo rather than microchip for the time being.
There is something more to this than Congress wanting to use the money to reunite Fluffy with little eight-year-old Johnny down the block. Although, yes, the government knows what you are doing via credit cards and the internet, but they cannot track your exact whereabouts. You don't have to buy into that either; you can always pay with cash. I want to be the one to decide whether I chip, tattoo, or do neither, not Uncle Sam.
Deena