I've been reading the posts about hotel swipecards with interest. I've always been fascinated about the level of information that goes into those keys, and more importantly how secure they are.

For example, if someone had a reader and writer, would they be able to rewrite the code that would let them into my room?

But what fascinates me more is what else is on the key, and what other information the hotel hold about me. I often use Marriot hotels and as a member of their rewards program they hold details about my room preferences (non-smoking, bed size, etc.) so that when I book, or simply turn up, I can get the room I want without having to tell them.