(FORTUNE Magazine) – Advertisers have made some dubious claims over the years. We've been asked to believe that buying a car is a patriotic act, that Burger King just tastes better (than what?), and that Michael Jackson drinks Pepsi (our money is on formaldehyde). But what about the obnoxious TV and radio spots that trumpet "prices so low we can't name them"? Are there really regulations that prevent advertisers from publicizing rock-bottom dollar figures?

The Federal Trade Commission, which regulates advertising, has no such prohibition, says Jeffrey Edelstein, a partner specializing in advertising at law firm Hall Dickler Kent Goldstein & Wood. Advertisers probably keep the prices to themselves because they hope to lure curious customers into their store, or they're reluctant to start a price war.

Doesn't that constitute false advertising? Don't look for the G-men to bust your local carpet emporium anytime soon. While advertisers that make blatantly untruthful claims can be fined by the FTC, Edelstein says this particular less-than-truth is what's known as puffery--and it's perfectly legal. "It's not something consumers would take seriously," he says. Advertisements lying? Next we're going to find out that Miss Cleo isn't really psychic.

--Reed Tucker