now i dont know how many people read this site in england but...
tesco is the largest chain of supermarkets in the uk, and now instead of getting 1% cash back with their clubcard you can get 1.2 ba miles per dollar (2.4/pound), in addition to your credit cards miles, by transfering your points on their website.
I've never heard of such a thing with stores' clubcards (do other stores do this?). we used to spend about $300 a month there and never used the card...