Apparently, Transport For London are planning ‘e-money’ trials based on their remotely-readable Oyster RFID cards.
Combine that with Kevin Mahaffey of Flexilis’ talk at Black Hat last year, where he demonstrated apparatus to extend RFID read range from 4-6 inches to approximately 50 feet, and things could get messy. ;)
The slides for that talk are available here (PDF); slide 20 specifically mentions the Hong Kong “Octopus” cashless-payment card.