Google Inc. is challenging Facebook Inc. by using a controversial tactic: requiring people to use the Google+ social network.

The result is that people who create an account to use Gmail, YouTube and other Google services—including the Zagat restaurant-review website—are also being set up with public Google+ pages that can be viewed by anyone online. Google+ is a Facebook rival and one of the company's most important recent initiatives as it tries to snag more online advertising dollars.

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