What Price Loyalty?

I was in Waterstones yesterday buying a couple of books. When I paid for them the person at the till asked me if I had a Waterstones "Loyalty Card". I said no and paid up. As I left the shop I began to worry about this.

Was it disloyal not to get a loyalty card? When you get one, do you have to swear an oath? If you get one of the cards and then buy a book from Amazon, do they mind? Can you get stripped of your card for such transgressions? Do they have loyalty police?

I think I had a near escape there...