I think the creepy feeling comes in that you don't realize the merchant is profiling you. At least not until they tip their hand a little too much (like sending you an entire booklet of nothing but maternity stuff).

You get a Safeway club card and you know full well that they're tracking you, because you hand them the card every shopping trip. Or you use Amazon or Netflix, where customers really want to be tracked -- the tracking and data mining are part of the draw, because they have such good suggestion engines.

I had LASIK a few years back and bought dry eye drops from Target - a lot of them, over six months time. Then my eyes healed and I quit buying it. A month later I get a coupon generated by a Target cash register for Systane drops, the exact brand I used to buy. I guess they thought I started buying them at Walgreens instead?

It was only when they gave me a coupon for a specific brand and product, that most of the population would likely not buy on a typical weekly shopping trip, that I realized all my purchases were being tracked and linked by my credit card number.

All that time before then, their prediction engine was selecting coupons for completely unrelated products, and I was using the coupons not even thinking about it.