According to comScore, total unique visitors to + in the U.S. went from 15.2 million in November 2011 to 27.7 million in June of this year. That's a jump of 82%.

Worldwide, Google+ visitors jumped from 66.7 million to 110.7 million in the same time period, marking a 66% increase, comScore reported.

"That's impressive," said Zeus Kerravala, an analyst with ZK Research. "I guess there is room for an alternative social networking vendor."

Google's social network had more good news earlier this month. The American Customer Satisfaction Index released a survey showing that while 's user satisfaction rating dropped 8% over the last year, to 61 on a 100-point scale, Google+, making its in the survey, scored 78.

Kerravala noted that Facebook may be the world's largest social network with more than 900 million global users, but the site has taken some major hits lately.