That's partly why the Federal Trade Commission urged Congress late last month to consider legislation that would force data brokers to explain to consumers how, when, and to what end, they collect information, as well as show what data they have. In late February, Obama pushed passage of his own "Consumer Privacy Bill of Rights that he says would give people more control over their online identity. Two firms, Acxiom and Experian North America, applaud the measures, saying added transparency won't inhibit their own microtargeting or political profiling. There's just too much information out there now.

Especially if people grant access willingly. Both Obama and Romney's sites allow, if not encourage, visitors to login to their campaign websites with a Facebook account, thereby unveiling a wealth of information: email address, friend list, birthday, gender, and user ID. Obama's team, in accordance with the president's call for greater transparency, details his campaign's privacy policy in an exhaustive 2,600-word treatise. It begins like an online Miranda Rights: "Make sure that you understand how any personal information you provide will be used." Then things get a little weird.

Among other points, the policy says the campaign can monitor users' messages and emails between members, share their personal information with any like-minded organization it chooses, and follow up by sending them news it deems they'd find worthwhile. In other words, target anger points. Then there's something called "passive collection," which means cookies -- lots and lots of cookies. Obama's campaign, as well as third-party vendors working with, spray trackers so other websites can flash personalized ads based on knowledge of the trip to barackobama.com. And finally, near the end of the policy, comes one more caveat: "Nothing herein restricts the sharing of aggregated or anonymized information, which may be shared with third parties without your consent."

Romney's site apparently wants even more from its visitors, asking users who login with Facebook to "post on (their) behalf" and "access (their) data any time" they're not using the application. You can deny both functions.

"Campaigns see this as war," said Joseph Turow, a professor at the University of Pennsylvania and author of the book The Daily You: How the New Advertising Industry Is Defining Your Identity and Your Worth. Each side vies for the most information to swell its own virtual catalogs. Republicans have Voter Vault. Democrats have Catalist after retiring the curiously-named "DemZilla."

At first, politicians eschewed microtargeting, arguing that tactics companies adopt would never win elections. But then George W. Bush clobbered John Kerry, who ran a sluggish campaign around labor unions and swing voters, and profiling started sounding like a pretty good idea. Now virtually every campaign, says Andrew Drechsler of Strategic Telemetry, employs the strategy. And, by all accounts, the technology hasn't even fully hatched yet.