Privacy advocates are resurrecting the spectre of subliminal advertising to battle against surreptitious corporate tracking of consumers' Web-surfing habits and preferences. Under fire is a widespread practice that uses special software to track Web surfers' visits and then places ads on their favourite Web sites or sends them email messages based on their preferences. In a hypothetical example, if an advertiser discerns from the tracking information that a consumer's favourite colour is pink, it could place pink ads on the Web sites to catch the consumer's attention, an online-marketing expert says. That amounts to subliminal messaging, privacy advocates say. The argument is the latest by privacy advocates searching for ways to prod regulators into greater scrutiny of such online marketing tactics. But the advertising industry says there is nothing subliminal about marketing based on online profiling. While consumers are targeted using information collected secretly, there aren't any secret messages in the appeals themselves. "Every time you make an 800 call or fill out a warranty card, you are becoming part of marketer's database," says Hal Shoup, executive vice president of the Association of American Advertising Agencies. The comparison with subliminal messages surfaced last month at a federal workshop on privacy issues. Jason Catlett, president of Junkbusters, which fights the marketing industry, told the gathering that "advertisers are using empirical behavioural science for individual mass-customised manipulation," comparing it with subliminal or hidden advertising that first came to light in the 1950s. Vance Packard's 1957 book "The Hidden Persuaders" exposed the practice and for years sparked waves of uneasiness in consumers and government officials as well as attempts to stop secret advertising. Among other things, movie theatres were accused of using subliminal messages -- appearing for a split second to encourage popcorn and soda consumption; a distiller's print ad allegedly included the word "sex" on an ice cube in a highball; and a toy company flashed "Get It" in a TV commercial. This week, privacy advocates took the latest fight to the Federal Trade Commission. Robert Ellis Smith, who runs a privacy newsletter, urged the commission to label profiling as an "inherently deceptive" trade practice. The FTC, he said, should "search its own precedents and discover that it has previously advised against advertising that is effectively identical to the kind of online profiling now at issue." But FTC officials said their files on subliminal advertising actually are very thin. Although there aren't any existing US laws against subliminal advertising, there is material suggesting that subliminal advertising may present a legal foothold for Messrs. Smith and Catlett in their campaign for regulation of profiling. Even though it hasn't issued any regulations, the FTC has taken the position that a subliminal ad "that causes consumers to unconsciously select certain goods or services, or to alter their normal behaviour, might constitute a deceptive or unfair practice." The Federal Communications Commission acted against the "Get It" ad in 1974, ruling that "broadcasts employing such techniques are contrary to the public interest". What do you think? Tell the Mailroom. And read what others have said.