It's not enough to "just do it" anymore. Now, you have to "just do it" online.

Athletic-apparel giant Nike (NYSE:NKE) has decided that the Internet needs a more central place in its advertising strategy. Rather than designing a traditional TV/radio/ billboard campaign and throwing in the occasional online banner ad, Nike wants to start with the digital message and build from there.

Trevor Edwards, Nike's VP of global brand management, says the days of one big ad and one big shoe are over. "Now you've got to engage consumers on every level," he said in a Wall Street Journal interview last summer. In that spirit, the company is ready to ditch its longtime advertising partner Wieden+Kennedy for a more digitally attuned firm.

For now, it's just one product line -- running shoes -- that's up for outside bids. But the agency itself recognizes that it is falling behind the digital times, and who knows where Nike's new train of thought will lead?

Perhaps the shoe maven developed a taste for pixels when Google (NASDAQ:GOOG) helped promote its soccer equipment through the World Cup site last year. The great thing about this sort of campaign is that you get to choose your customers and draw them in with exclusive content that attracts exactly the sort of consumer you want in your stores. Your marketing message can be highly personalized and much more effective than the old mass-market broadcast tactics were.

Google and Yahoo! (NASDAQ:YHOO) both have started to zone in on this thinking, and they are emerging as leaders in this new wave of advertising expertise. They certainly aren't marketing agencies in the traditional sense of that term. Instead, they're reshaping how enormous advertising clients such as Nike, General Motors (NYSE:GM), and Coca-Cola (NYSE:KO) are thinking about their promotional activities.

These are still the early days of online marketing, and perhaps it's a bit too soon to crown a champion. But when you consider the amount of cash flowing around the global ad industry every day, it doesn't take much of a market share to generate some serious income. Do you still think Google looks expensive?

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Fool contributor Anders Bylund is a Coca-Cola shareholder but holds no other position in any of the companies discussed here. You can check out Anders' holdings if you like, and Foolish disclosure is always tasty.