RFID Chips and Viruses
Of course RFID chips can carry viruses. They’re just little computers.
More info here. The coverage is more than a tad sensationalist, though.
EDITED TO ADD (3/16): I thought the attack vector was interesting: a Trojan RFID attacks the central database, rather than attacking other RFID chips directly. Metaphorically, it’s a lot closer to biological viruses, because it actually requires the more powerful host being subverted, and there’s no way an infected tag could propagate directly to another tag.