It could take 300 years to index all the world’s information and make it searchable, Google Chief Executive Eric Schmidt predicted on Saturday.

“We did a math exercise and the answer was 300 years,” Schmidt said in response to an audience question asking for a projection of how long the company’s mission will take. “The answer is it’s going to be a very long time.”

Of the approximately 5 million terabytes of information out in the world, only about 170 terabytes have been indexed, he said earlier during his speech.

Schmidt admitted to the audience of advertisers that when he first arrived at Google four years ago, he viewed ads from a skeptical consumer standpoint. Shown ads on Google, he thought “You’ve got to be kidding! People actually click on this stuff? And they do.”

He said he quickly realized, though, that “ads actually do have value if you can figure out the right ones to show.”

Technology and the interactivity it enables, such as the ability to measure an Internet ad’s success rate by viewing how many people click on it, is shifting power in the advertising industry from executives at corporations to consumers, he said.

“The power is moving from us to the end user; it’s occurring by the power of the personal computer, by the power of the cell phone,” he said. “Thirty years ago we would make the decision (about ads). Now, that person, that individual makes that decision.”

Advertising is increasing on the Internet and cable television, and showing modest to no growth in newspapers and magazines, Schmidt said. “The cost per revenue dollar of online ad systems is so much lower than” for offline advertising, he said.

Of the estimated $283 billion spent on advertising in the United States, $11.3 billion is spent on the Internet, with Google taking in about 1 percent of that, Schmidt said.

Despite the slowdown in print advertising, Google is testing a campaign in which the search giant is using its audience targeting technology to help customers place ads in magazines, he said.

Schmidt predicted there will always be ads on the Internet but that there may be an “ad-free subset” of the Internet that might offer a different way for people to pay for things, such as using micro-payments.

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