There is a new debate starting about the possible dangers of microchips. At this time it may be best to get your vet to tattoo your pet instead of microchipping. Tattooing may have many advantages over the chipping. Microchips do not always work and they tend to migrate. Also a tattoo can be removed, but a microchip is more difficult to remove. Also many pets end up getting killed because the chip never showed up on the scan, or that shelter doesn't have a scanner.
A series of veterinary and toxicology studies, dating to the mid-1990's, stated that chip implants had "induced" malignant tumors in some lab mice and rats. Fibrosarcomas and Liposarcomas have been reported in dogs at the site of an implanted microchip.
To read what a vet has to say on the subject of microchips, go to: www.thepetwhisperer.com/MicroChips.html.