Executives with consumer review site Yelp and comparison shopping site Nextag told senators Google's search practices are hurting their businesses. Instead of innovating, Google has copied other services in creating its own shopping site, said Jeff Katz, CEO at Nextag. About 65 percent of Nextag's search results come through Google, and recent changes to the Google search results have dramatically hurt his business, Katz said.

Google was a good partner for years, but it has recently begun to favor its own services over Yelp, said Jeremy Stoppelman, Yelp's cofounder and CEO. Google in recent years has focused on being a destination site, not an unbiased search engine, Stoppelman said.

Stoppelman questioned if Yelp could succeed today, under Google's current practices. Asked if he'd start Yelp in the current environment, Stoppelman said, "I'd find something else to do."

But Google users can easily choose another search engine or other services, if they don't like the end results, said Susan Creighton, a partner with the Wilson Sonsini Goodrich & Rosati law firm and an antitrust adviser to Google. Amazon.com provides a huge product search service and Facebook has a large local advertising service, she said.

"It's free and instantaneous to try someone else's search results," she said.