How to Exercise the Power You Didn’t Ask For

I used to be largely indifferent to claims about the use of private data for targeted advertising, even as I worried about privacy more generally. How much of an intrusion was it, really, for a merchant to hit me with a banner ad for dog food instead of cat food, since it had reason to believe I owned a dog? And any users who were sensitive about their personal information could just click on a menu and simply opt out of that kind of tracking.