May 18, 2009

For decades, the nation’s biggest antitrust cases have centered on technology companies. And they have all been efforts by the government to deal with powerful companies with far-reaching influence, like AT&T, the telephone monopoly; I.B.M., the mainframe computer giant; and Microsoft, the powerhouse of personal computer software.

Last week, the Obama administration declared a sharp break with the Bush years, vowing to toughen antitrust enforcement, especially for dominant companies. The approach is closer to that of the European Union, where regulators last week fined Intel $1.45 billion for abusing its power in the chip market.

In this new climate, the stakes appear to be highest for Google, the rising power of the Internet economy.

The new antitrust leadership, legal experts say, is likely to scrutinize networks — technology platforms that become so dominant that everyone feels the need to plug into them. The advantages to the companies that control such networks snowball as they attract more users, advertisers or software developers.

Internet search and search advertising, like personal computer operating software, is one example, said Herbert Hovenkamp, an antitrust expert at the University of Iowa law school. “Google is a dominant network, as is Microsoft,” Mr. Hovenkamp said. “Networks become competitive only if everyone has the same chance.”

Google’s corporate behavior is already being closely monitored. Last year, Google abandoned a planned search advertising partnership with Yahoo after the Justice Department said it intended to file suit to block the agreement on antitrust grounds. Google has 64 percent of the Web search market in America, while Yahoo has 21 percent and Microsoft 8 percent, according to comScore, a research firm.

In recent weeks, antitrust officials have opened two inquiries. The Justice Department is looking into Google’s settlement with authors and publishers for its book-search service to see if it violates antitrust laws. And the Federal Trade Commission is examining whether Google’s sharing two board members with Apple reduces competition, because both companies offer Web browsers and phone operating systems.