I have to say that Oyster cards are such a brilliant idea that I did NOT use one for several years....I assumed it was another useless product of the buffle-headed dandiprats who have taken over just about all aspects of life in UK. When someone told me that they are actually a good thing, I could not believe or understand how the brain-dead bureaucrats at TfL had managed to come up with something genuinely useful for Londoners and occasional visitors!