The little ads that could

Those goofy little text ads next to your Google search represent a rapidly growing $4 billion industry, according to a new study from the Search Engine Marketing Professional Organization, another unbiased group if ever we saw one.

Although these four-line, all-type ads don't have the same graphic appeal as a Macy's double-truck* ad for women's underwear, advertisters love them because they are highly targeted and their performance is instantly measurable. Best of all, they provide absolute, fine-grained control: You can change the copy and turn them on and off at will.

Advertisers even can put their ads opposite a search for their competitors. Thus, Canon can buy an ad next to a search using the key word "Nikon." This practice was challenged in the courts but the judge said it was OK for the fun to continue.

* A double-truck ad is two full facing pages in a newspaper.