I wonder if something like this is really that far away from reality. I certainly hope not.
The technology is all available today. All the information they are referring to is entered in various computer systems and much of it is public records. The logic behind is not complicated at all. In fact, I could probably write an application like that in very little time, given access to the databases. A universal ID like in the ad would make it much easier, but even without it it's no big deal.
The current laws do limit access to medical information, and that has been made stricter recently with the HIPAA act. I don't think that there's a chance that this information would ever become available to a pizza parlor.
The real key, however, is the access to the credit card data on the level of individual purchases. I am not sure if that information is at all protected. It's not your financial data, strictly speaking, is it? If the merchants find a way to share that, it would not be hard to infer the state of your health from your buying habits.
hal, I'm curious to hear what ACLU is pushing, in your opinion. From what I know about them, they seem to be pretty evenhanded, taking cases on both sides of the political spectrum (someone in Manwe posted examples a while ago). If they seem to be taking up a liberal cause more often, perhaps it illustrates which rights and interests require greater protection these days.
As for people being able to stop something like this... that's a topic for another forum. Market forces might come into play, if consumers plain refuse to deal with businesses that infringe on their privacy. But the way many markets are consolidated now, how much choice do we really have?