Inserting RFID-chips (and other material?) into a body (human or animal) raises the change of starting cancer. "A 2006 study in France detected tumors in 4.1 percent of 1,260 microchipped mice. This was one of six studies in which the scientists did not set out to find microchip-induced cancer but noticed the growths incidentally. They were testing compounds on behalf of chemical and pharmaceutical companies; but they ruled out the compounds as the tumors' cause. Because researchers only noted the most obvious tumors, the French study said, "These incidences may therefore slightly underestimate the true occurrence" of cancer."

I was interested in tests of implanting humans with rfid etc, so i wonder where this ends, and hope (and assume) it will be solved.