A relevant message is critical if the behavioral-targeting equation is to equal success. But, according to Calvin Lui, CEO of customized ad solutions provider Tumri, some marketers don't pay enough attention to the relevancy side of the equation. "If you spend the money, the effort, and the technology to find these segments, why would you show each of the segments the same message?" Lui asks. "You want to tailor your message to each of the segments. You've got to go that last mile."

Solutions are available that enable customized display ads to be constructed on the fly, based on targeting or performance data. So an automotive ad for a surfer in Los Angeles might feature a convertible, a beach in the background, and a lifestyle-focused headline, while an Indiana soccer mom may receive an ad from the same automaker featuring a minivan, a rural background, and a safety-oriented headline.

ValueClick's Ardis agrees that dynamic messaging, in conjunction with effective targeting, is key to a successful outcome. "To combine the strength of targeting methodology with behavioral offers, we've really confined the audience to those who have the best shot of being interested," he says. "And then, once you find them, you deliver a very granular, pretty much one-to-one offer or messaging to them. It really puts it on a different level. It takes an already strong approach and makes it stronger."