An article in Wired Magazine (http://www.wired.com/wired/archive/3.09/updata.html) asks just this question. It points out that in the dealer agreement, the manufacturer of the embedded chip technology available to identify pets specifically forbids placing chips under the skin. This technology is already being used in ID tags for wandering residents of nursing homes, in lift tickets at ski resorts, and in parking passes and other objects.

Another article to check out is: http://www.wired.com/wired/archive/1.04/desire.to.be.wired.html