Awhile back Lori Andrews, the forward-thinking Kent Law expert on the intersection between law and technology, wrote a much-discussed editorial on the data we voluntarily give Facebook and Google, how they use that, and by extention us. It's a question worth asking, though the answer isn't obvious: Facebook is a powerful tool offered to us for free; it's powerful because of its immense reach; and its immense reach is due to the fact that it costs nothing.

Instead of paying with money, we pay with information. It's a more opaque transaction than paying with money, which is part of the concern for privacy activists. But we also give information when we pay with money. And that information can be a lot more valuable, and personal, than the information we willingly offer up instead of money.

I was reminded of Andrews's piece when I read "How Companies Learn Your Secrets," Charles Duhigg's fantastic New York Times Magazine story. You've probably heard of it because of the part about how Target knew a high-school girl was pregnant before her dad did. How'd they know? Shopping habits—Duhigg's piece is as much about habit as it is about, heh, target marketing—and years upon years of cataloging them.

The desire to collect information on customers is not new for Target or any other large retailer, of course. For decades, Target has collected vast amounts of data on every person who regularly walks into one of its stores. Whenever possible, Target assigns each shopper a unique code — known internally as the Guest ID number — that keeps tabs on everything they buy. “If you use a credit card or a coupon, or fill out a survey, or mail in a refund, or call the customer help line, or open an e-mail we’ve sent you or visit our Web site, we’ll record it and link it to your Guest ID,” Pole said. “We want to know everything we can.”

Also linked to your Guest ID is demographic information like your age, whether you are married and have kids, which part of town you live in, how long it takes you to drive to the store, your estimated salary, whether you’ve moved recently, what credit cards you carry in your wallet and what Web sites you visit. Target can buy data about your ethnicity, job history, the magazines you read, if you’ve ever declared bankruptcy or got divorced, the year you bought (or lost) your house, where you went to college, what kinds of topics you talk about online, whether you prefer certain brands of coffee, paper towels, cereal or applesauce, your political leanings, reading habits, charitable giving and the number of cars you own.

None of this is new, of course; the point of Duhigg's piece is more about how we're developing a much more detailed understanding of habit, which includes better interpreting this data that's been collecting for years and years. For instance, I recall a brief boomlet in people trading customer-loyalty cards to confuse corporate Leviathans (while still getting the discounts). I have three such loyalty cards on my keychain, so it obviously didn't sink in.

This in turn reminded me of a fascinating Slate piece by Sasha Issenberg on Obama HQ and the leap in sophistication the campaign's tech team—led in part by former Threadless CFO Harper Reed and Edelman's Michael Slaby, both of whom would have been candidates on my list of the city's most powerful—has taken in voter targeting. Meet Project Narwhal:

It was a message that sat well with the young Ohioan who received it. She was single, liberal, sensitive to medical costs—but she had never told the campaign any of those things, and the one piece of information she had provided (her ZIP code) could easily mark her as the type of traditionalist Midwestern woman who would recoil at efforts to liberalize access to birth control. Indeed, she found it hard to believe that many other residents of her ZIP code would look as favorably upon a rallying cry to defend Planned Parenthood as she did.

Project Narwhal is both groundbreaking and not. The most interesting thing—to me—that Issenberg found was that it mainly puts together a lot of existing information that the campaign has, but that wasn't talking across databases. (If you're surprised that a tech group as lionized as the 2008 Obama campaign was "manually moving individual bits from one database to the next," you haven't worked in or closely with IT in the Web era.) In my experience, this is what virtually every large organization has been going through over the past decade: getting piles of information that reside in kludgy, primitive databases and translating them all into the same language. Our understanding of what to do with data with regard to habit has grown—compare Project Narwhal with McGovern boy-wonder and Midwestern organizer Gene Pokorny trying to flip twos and threes to his candidate in Chicago in 1972. Porkorny himself later became a marketing research exec. But the raw technical part is a huge piece.

The pieces by Duhigg and Issenberg also seemed in sharp contrast with what little Google and Facebook know about me, and a lot of other people who have gone through their profiles. Target can predict when a woman is pregnant; the Obama campaign can locate a birth control advocate in a conservative ZIP code. Google, which I use hundreds of times a day, has my gender right and a couple broad interests, but is 24 years off on my age.

Google, Facebook, and other free web sites are at the center of a lot of privacy discussions, but I can't help but think they have a long way to go before they know as much about us as a lot of old retail shops. Not just because they're new, but because the data set of stuff I do on the Internet, in some ways, says a lot less about me than the stuff I actually commit money to. What I do on Google and Facebook represents a lot of the noise in my head. When I swipe my credit card, that shows I care.