Marketing data provider Acxiom is bringing to the Internet the consumer profiles for which it and other data providers are known among direct-mail companies and telemarketers - who prize knowing where to find "early parents," "penny pinchers" and other types of households for credit-card promotions and other offers.
Privacy advocates are taking notice.
"It violates average users' expectations," said Ari Schwartz, deputy director of the Centre for Democracy and Technology. "It's such a sea change in the way users use information online."
The popular online hangout Facebook recently learned that there's such a thing as too much targeting.
Users protested when the company launched a marketing program that lets companies target messages based on what their friends buy and do online. Facebook retreated twice - first by making sure users give consent to sharing data, then a week later by letting users turn it off completely.
So far, there hasn't been a similar outcry over Acxiom's program, although the company has refused to disclose which companies it sells ads for or are partnering with it in other ways.
Like other data brokers, Acxiom routinely mines phone books, voter lists, property records, warranty cards and other data to profile and categorise your household and about 130 million others across the country into 70 categories.
Relevance-X, the new online program Acxiom launched in October, taps those "life stage" categories to target advertising.
Now, when you give your name and address to an online retailer, survey service or other website partnering with Acxiom, the company will match you against its offline records - unless you specifically decline sharing.
And then it will tag your computer with a "cookie" identifying your life stage and match that with the type of site you are visiting to determine which ad to show.
Jennifer Barrett, Acxiom's global privacy officer, said Acxiom clients familiar with segmentation offline had expressed interest in applying the techniques online.
The program, she said, would help consumers cut through online clutter and get ads most likely to appeal to them.
"This allows advertisers to do a better job," Barrett said. "If you are selling children's toys, you either want to sell it to people with kids or grandchildren."
Acxiom isn't the first company to try to combine online and offline information or target ads to an individual's buying or browsing habits.
In 1999, when Internet advertising firm DoubleClick bought Abacus Direct, it gained direct-mail databases that enabled it to match ads with individual buying habits, on top of its ability to display ads based on the type of website an Internet user is visiting.
Amid criticism, DoubleClick ultimately backed away from such razor-sharp targeting, however.
Barrett said Acxiom designed its system to account for the complaints against DoubleClick, which Google has announced its intention to buy for $3,1-billion.
"The company is trying to respond in a reasonable way," Barrett said, "without trying to amass too much data to make consumers feel uncomfortable and that they are living in a surveillance society."
Acxiom is safeguarding users' privacy several ways, she said. For one, the cookie doesn't transmit your name or address - just attributes about your interests. And "we can't ever go back and reconnect that with personally identifiable data."
Barrett also said the company doesn't create profiles based on an individual's browsing history. It targets ads only to the site the person's currently visiting.
Users worried about privacy can remove themselves from the program, she said. They can "opt out" either at Acxiom's website or by calling a toll-free phone number.