When financial cryptography = PAIN

Physical pain that is.

Ironically, rather than protecting their wearers from kidnapping, implantable security devices may actually turn their wearers into tempting targets for Mexico's notorious kidnapping gangs, especially as the chips migrate to serve as payment devices, says Albrecht. "What could be more inviting to kidnappers than a chip that offers access to secure areas or someone's bank account? If criminals want to get ahold of a chip, they will naturally try to nab a person wearing one."
The potentially gruesome implications of being probed for an implanted chip are obvious, said Albrecht. She points out that at least one Mexican kidnapping gang, a group nicknamed "el chip" for its interest in RFID implants, is focused on the technology. According to recent reports, its members have stripped kidnapping victims and demanded to be told where they have chips implanted in their bodies. 

As a side note seats are still available at the 'RFID Academy Australia' 29-30 July 2004 held by Alien Technologies http://www.alientechnology.com/01_rfidacademy_p05.html They don't seem to have any financial issues addressed just tracking, still if you have excess amounts of money to spend listening to their markting you may want to book in.