Numbers

I'm reading a book by Jeffery Deavers right now that is scaring the crap out of me. It's a murder mystery but it's not the murders that is scary....it's the midis operandi - he uses data to find his victims and he uses data to frame innocent people for the crimes.
I know this is far fetched, but working with computers and databases and knowing what I know about RFID, data mining, and data collection, it brings into focus the topic of personal privacy.
Those supermarket discount cards that you swipe each time you check out tells a great deal about you and your family. Warranty cards are just a means of collecting data because the warranty is good whether you fill out a card or not. Any time you fill out a survey or divulge private information, that stuff ends up in a database somewhere.
Using sophisticated software, you can tell a great deal about people from data that seems unimportant. Data miners can ascertain whether you are likely to buy expensive brand names or generic, the kinds of food you buy at the grocery store could predict, to some degree, how healthy you are. Someone that buys a lot of sweets, snack food, meat, beer and cigarettes would probably have a tendency to be less healthy than people than people who buy a lot of fruit, vegetables, and vitamins.
I studied quantitative analysis in grad school and I know that numbers can be misleading, but they can also be very revealing.
So, what do we do? I'm not sure what the answers are, but I have to believe that the less people know about your personal business, the better.