A recent report, by the Council On Ethical and Judicial Affairs of the American Medical Association looks at the use of RFID. While it acknowledges that there are no real medical risks, the report seems to confuse the current version of implantable RFID tags with other types of RFID tags. And, while the report doesn't really sound any real alarms about RFID, it's being reported by some media, at least in the headline of some articles, that the report highlights "significant risks."
Source: AIM Global, http://www.aimglobal.org