Promos don't have to be targeted to people based on their past buying patterns. Offering different promotions, discounts, and so on to randomly selected groups of people, to see how well they work for the sample, is a standard way of evaluating options before offering them to everyone (or deciding they're not a good idea). There's nothing unethical, or remotely illegal, about it if the terms and conditions are stated up front, as they seem to have been for the CBSnn set. (There was a flap last year when amazon.com gave people different prices for the same book, and didn't tell them they were doing it; that's another story.) If they let anyone who hears about a promo sign up for it, it would screw up the results.

So, much as I'd also like to sign up for every Citibank test promo anyone mentions on FT, it ain't gonna happen - and we don't have a real basis for complaining about it.