First, thanks for many years of enjoyment from marginal revolution!
Second, I thought you would find it interesting that Safeway’s new “club” program (called Just for U) apparently uses shoppers’ purchase histories to offer household-specific prices. From the FAQ (italics added):
Why don’t I automatically get these offers?
Our systems use your purchase history to sort through and organize personal price offers, hundreds of coupons, and all of our weekly Card Specials. But only you can determine if our systems got it right.
That’s why we ask that you select offers by loading them to your Club Card. As you provide feedback based on what you select, our systems will improve their ability to sort through and personalize your offers. This will make the program even more valuable to you over time!
Why don’t you just give me these prices in the store?
If every shopper were exactly like you, we could! But the reality is every Safeway customer is different. This program is personalized just for U!
TC again: And via Justin Wolfers, Orbitz steers Mac users toward pricier hotels.