Tracking your movements: the world's their Oyster

Here's a thing. I knew Oyster cards kept records of their user's movements around the Tube and bus networks; what I didn't realise is how easy it is to get at that info. All you've got to do is find out what the card's serial number is and borrow the user's PC; doesn't everyone tick 'Remember me' these days?

I use the Tube network a lot, and the detail of just knowing which stations I've been through, and when, would tell someone pretty much everything they needed to know about my day - so I've decided to switch to an anonymous card, although they requre some sleight of hand to get hold of.