Schmidt's answers didn't seem to assure Lee, either. Schmidt's answers confirmed his "fears" of Google search bias, Lee said.

Questioned about the rankings for some small businesses rising and falling in search results, Schmidt told senators that Google tweaks its search results about 500 times a year. Google is providing a good service for the "vast majority" of small businesses in the U.S., he said.

"Not every website can come out on top," Schmidt said. "For every winner, there's a loser."

Google's search business model seems to have changed in recent years after an "acquisition binge" has brought the company into several new markets, said Senator Herb Kohl, a Wisconsin Democrat and subcommittee chairman.

Senator Richard Blumenthal, a Connecticut Democrat, compared Google's early business model to a company that owned a racetrack but then began owning horses. "Your horses seem to be winning," he said.