Neill Wood wrote to uk.transport.london on Wed, 1 Sep 2004:

A thought has occured to me while reading this thread. People get on
buses and swipe their Oyster cards without removing them from the
wallet. Is there any indictation apart from the bleep to the driver
that the card is genuine? If you were to have a fake card you can just
pass it in front of the reader and get on free. If the driver is busy
or there is a lot of noise he's got going to hear the bleep. If an
inspector gets on, do you only have to flash you card at him? Have I
uncovered a major fraud possibility here?

Normally the inspectors have hand-held readers that read your card for
you, and tell them what you last swiped and when.

What I want to know is, do you have to take the card out of your
handbag/wallet to use it? I know it can/should be used in its own
wallet, but on the Continent, where similar systems are in use, you see
people just brushing their bags against the reader, not bothering to
take the card out at all. I don't know how many layers will inhibit
reading!
--
"Mrs Redboots"
http://www.amsmyth.demon.co.uk/