MOUNTAIN VIEW, Calif. — When Larry Page and Sergey Brin founded Google Inc. on Sept. 7, 1998, they had little more than their ingenuity, four computers and an investor's $100,000 bet on their belief that an Internet search engine could change the world.

It sounded preposterous 10 years ago, but look now: Google draws upon a gargantuan computer network, nearly 20,000 employees and a $150 billion market value to redefine media, marketing and technology.

Perhaps Google's biggest test in the next decade will be finding a way to pursue its seemingly boundless ambitions without triggering a backlash that derails the company.

"You can't do some of the things that they are trying to do without eventually facing some challenges from the government and your rivals," said Danny Sullivan, who has followed Google since its inception and is now editor-in-chief of SearchEngine Land.

Google's expanding control over the flow of Internet traffic and advertising already is raising monopoly concerns.

The intensifying regulatory and political scrutiny on Google's expansion could present more roadblocks in the future. Even now, there's a chance U.S. antitrust regulators will challenge Google's plans to sell ads for Yahoo Inc., a fading Internet star whose recent struggles have been magnified by Google's success.

Privacy watchdogs also have sharpened their attacks on Google's retention of information about the 650 million people who use its search engine and its other Internet services like YouTube, Maps and Gmail. If the harping eventually inspires rules that restrict Google's data collection, it could make its search engine less relevant and its ad network less profitable.

To protect its interests, Google has hired lobbyists to bend the ears of lawmakers and has ramped up its public relations staff to sway opinion as management gears up to conquer new frontiers.

In the latest example of its relentless expansion, Google has just released a Web browser to make its search engine and other online services even more accessible and appealing. Not every step has gone smoothly, though; several of the company's ancillary products have flopped or never lived up to the hype.

Extending Google's ubiquity to cell phones and other mobile devices sits at the top of management's agenda.

But the lengthy to-do list also includes: making digital copies of all the world's books; establishing electronic file cabinets for people's health records; leading the alternative energy charge away from fossil fuels; and selling computer programs to businesses over the Internet.

"There are people who think we are plenty full of ourselves right now, but from inside at least, it doesn't look that way," said Craig Silverstein, Google's technology director and the first employee hired by Page and Brin. "I think what keeps us humble is realizing how much further we have to go."

Page and Brin, both 35 now and worth nearly $19 billion apiece, declined to be interviewed for this story. But they have never left any doubt they view Google as a force for good — witness their corporate motto: "Don't Be Evil."