Some time ago I read about a Japanese plan to attach RFID tracking devices to Osaka schoolchildren, and I thought I linked to it here but can't find the item even with my spiffy search page. Now the Americans (well, Californians) have picked up the idea, and the ACLU is in a tizzy (linked document is their press release redistributed by EFF). RFID tagging of human beingss also drew attention recently when Bruce Schneier was trolled by some Danish artists who pretended to have a long-distance RFID-implantation rifle for sale. Read the comments on that one to see me give an incorrect derivation for "jumping the gun" and a lot of other silly folks confuse that phrase with "jumping the shark".
UPDATE: The program has been cancelled by the company that was sponsoring it, with little explanation.