You make a lot of excellent posts here, but I have to disagree wholeheartedly with your entire argument on this subject. (I will preface this by saying that it's entirely possible an unscrupulous company could do the things you've suggested, but a reputable company won't.)

I've worked in the US retail industry for quite a few years now and I can tell you that the reason companies use discount cards is to build loyalty. The idea is that if a person needs to stop by a grocery store (or whatever the need) he or she will forego a store that may be more convenient to access in favor of one in which he or she can get a discount or build a reward on the purchase.

Do companies spend millions of dollars on this technology? YES. But they don't do it to steal your data, they do it to make sure you spend your money in their stores. Why would a company care about a woman's menstrual cycle or any other type of info along those lines? What would be the benefit? Are they going to send a happy little message saying, "Congrats on your latest period!"? Or, for the guy who purchases a pack of condoms, "Woohoo! We're happy for you! Is it a girlfriend or just a fling?"

I've worked for some of the largest retailers in the US, many of which offered discount cards and nothing was ever asked of the customer but very basic information, such as name and address, and this is for mailing purposes since most cards offer rewards in the form of mailed coupons and the like beyond the discounts available in the store.

I have never seen a card, whether in a store I worked or one I shopped, that required me to give any personal details such as my Social Security number or credit card number. If I were ever asked for that type of info just to get a discount, I'd happily skip the discount.

I will add, lastly, that your view of the retail industry is very, very flawed. Companies aren't offering huge discounts after taking huge markups - that's illegal and closely regulated. They are offering huge discounts because the global economy is weak as a result of many variables and they need any sales they can get.

Conspiracy theories make for good fodder, but they don't hold water.