I just got this email from the Neighborhood watch of Menomonee Falls on this new trick to steal credit card numbers just by walking passed you on the street. 
http://www.wreg.com/videobeta/?watchId=8ba6f8fc-90a2-4711-90ea-1884ec348310

The scary part is with enough power with an antenna a person can activate and read an RFID chip from several feet to several yards away.  A person could sit at a food court at the mall or Summerfest and clean up.

I heard about the dangers of RFIDs about a year ago when talking about them in passports and how it could be used to target US citizens traveling in foreign countries as a trig for a bomb.  Back then they couldn’t read the info in the RFID.  Well it looks like they can at least read credit cards now.

http://www.engadget.com/2006/08/18/scaremongers-dub-rfid-passports-as-potential-bomb-trigger/

I guess those tin foil hats should be on our wallets.