Apparently, Transport For London <a href="http://software.silicon.com/applications/0,39024653,39150647,00.htm”>are planning ‘e-money’ trials based on their remotely-readable <a href=’http://www.rfidbuzz.com/wiki/Standards/MIFARE’>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.