The Stealthy Sell

Go to a beach party in Spain or tune into Belgian radio, and you're likely to hear one word: "Chihuahua!" This is not a forlorn pet owner summoning his tiny, unimaginatively named dog. It is the sound of marketing, the remix of an old mambo song that has gone from TV spot to hit single and the word on millions of lips. And it's all brought to you by Coca-Cola — not that you'd know from listening to the song.

In a cluttered marketplace, advertisers need to be different. Traditional ads repeating a brand name 30 times in...