THE popularity of Google’s search engine in the United States just grows and grows. In the past three years, its market share gains have even been accelerating, making some people wonder whether the company will eventually obliterate what remains of its competition in search.

Certainly, antitrust scrutiny is a growing worry at the Googleplex. Last year, the company abandoned a proposed advertising pact with Yahoo when the Justice Department said it would file an antitrust lawsuit to block the deal. Last week, a small Web site operator, TradeComet.com, filed an antitrust suit against Google, accusing it of unfairly manipulating its advertising system to harm a potential competitor.

And when I asked to speak with Google’s chief economist about why Google’s market share gains were accelerating, Google’s press office also gave me, unrequested, a second, separate appointment with Dana Wagner, the company’s “competition counsel”  that is, its point person on antitrust issues.

Google maintains that its lead in the Web search market is tenuous, saying that with a simple click of a mouse, a user’s loyalty could evaporate at any moment.