Here’s another reason why the blogosphere’s vision of the web as an open marketplace likely won’t come to pass: the BIG advertisers won’t finance it.

Let’s face it, the Googlenomics revolution has been financed by the little guys, who have profitably grown their businesses with pay-per-click ads. For small companies, brand management is secondary to driving sales. Not so for the big, bad corporate advertisers.

There’s a reason why Google bought a stake in AOL. From OnlineMediaDaily, we learn:

Mike Kelly, president of AOL Media Networks, told OnlineMediaDaily that one of the main benefits of the company’s new arrangement with Google is that AOL’s sales staff now will be able to offer clients the ability to buy search ads just on AOL properties.

Some search engine marketing executives say that the ability to ensure that pay-per-click ads are displayed on specific properties will encourage large marketers to spend more on search.

“It’s definitely a plus for marketers to have the flexibility to buy on AOL alone,” said Joshua Stylman, managing partner at Reprise Media.

Gregg Stewart, senior vice president, channel management and marketing at Fathom Online, agreed. “Marketers will always want to go for precision if given the opportunity.”

What’s more, Stylman added, many marketers think AOL has “cleaner” traffic than other networks; AOL’s subscriber-only past has created at least the perception that the network reaches real people, as opposed to bots or spammers. But, he added, marketers would do well to test their campaigns and determine which properties yield the better results. Not all campaigns will do better on AOL, said Stylman, adding that some marketers will have better results on Google’s network.

Big advertisers have been around a long time and know better than to practice unsafe advertising — and to put themselves at the mercy of click fraud (although they do buy TV advertising, so they’re not always geniuses of accountability).

Keep in mind why communism is flawed in theory — people (media consumers) don’t want total control, and those in power (big advertisers) don’t want to lose control.

As technology unravels old media business models, the result won’t be a completely open marketplace. A handful of brands will still dominate — those that people trust.

Welcome to the trust economy.