h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Oyster is now a very much mainstream way of traveling on London transport.
Word of warning: The card has a wire running near the edge of it all the way round. If this is broken the card will cease to function so if you have it in a wallet where the end sticks out and takes a lot of abuse you could crack the card - at which point it will cease to work. If it was registered take it to the nice people in the ticket office they will get it replaced for you free of charge with a minimum amount of paperwork. You have to pay for the replacement of lost cards.

It is a good idea to register your Oyster so that if/when you lose it you can have your old balance transferred to your new card. You don't have to register your card if you want to remain anonymous but you do lose this benefit by not registering.

There has been discussion of using Oyster like the Mondex card that was trialled in Croydon in the 1990s. If this goes ahead the money stored on the card can be used for a wide variety of purchases just like cash in a purse or wallet. So purchasing reading materials, drinks and food could also be done with an Oyster card while at a station.