Google has made a fortune selling ads. Now it is trying to put its hundreds of millions of users to work as company pitchmen, using the profiles, pictures and recommendations of ordinary people to endorse products and services across the Web.

After the policy takes effect Nov. 11, users who review a video on YouTube or a restaurant on Zagat.com could see their name, photo and comments show up in ads on any of the 2 million websites that are part of the company's display advertising network.

The controversial practice, announced Friday by Google, is part of an emerging trend on the Internet. Advertisers believe that consumers place enormous value on product endorsements that come from a friend or family member, and growing numbers of Web companies are trying to capture that social advertising in a systematic way.