(Wow! Two posts in one day!)
I was reading an article in this week's Yated about the activists who have started insisting that stores in B'nei Brak must sell only clothing that appeals to certain standards or not be placed on a "white list" of stores where chareidim there may not shop.
The activists (known as the Vaadas Hapikuach Lechanuyos) brought a list of stores who have complied to Rav Aharon Leib Shteinman. According to the article (bolding mine):
HaRav Aharon Leib Shteinman read through the list with obvious satisfaction and wondered aloud how there could be chareidi store owners who have not yet joined the program. HaRav Wosner said he was pleased be'ezras Hashem there are now clothing stores where Jewish women can shop without concern, and expressed confidence additional store owners would join the program. HaRav Nissim Karelitz, who has guided the organization since its founding, encouraged the delegates and suggested a course for further activity.
I find it interesting that the path of action to take was to pressure the stores, rather than to pressure the individual buyers. If one were to successfully pressure the individual buyers, then the buyers would not buy the items and the stores would not sell them. The most obvious example would be a store that sells ham (among other items) in an exclusively Jewish neighborhood. Since no one is going to buy the ham, eventually the store owner would see the futility of carrying it and stop doing so.
It would seem to me that the need to pressure the stores stems from a failure of the activists to pressure the people individually. Since they can't (or won't) tell their women not to buy certain articles of clothing (or the women won't listen to such instructions), they feel that they must remove the opportunity to buy them.
Of course, however, that, too, is a failing proposition. While it may make it more difficult for women to shop for clothing that they want, it certainly won't prevent them from doing so entirely. One can always drive or hop on a bus and go to the next town to find clothing, purchase it through mail-order or the internet, or some other way.
In short, if you want any sort of ban to succeed, you have to first win over the will of the people. If you can convince the people that the ban is necessary, then you won't have to resort to pressuring shopkeepers - economics will take care of the problem for you. If you can't convince the people of the necessity for the ban, then, in today's global market, pressuring the shopkeepers will harm no one but the shopkeepers.