Just a month after the launch of Google+, the social site has gained immense momentum. A survey from YouGov shows that Google+ is likely to be the second most popular U.S. social network by the mid-2012 YouGov used a sample of 1,003 U.S. residents that comprised a representative selection of U.S. Internet users. They were interviewed from July 29 to August 2, just over a month after Google+ first launched. In that month, Google+ had already scaled up to an estimated 20 million-plus users. In the U.S., Google has already achieved 13 percent market penetration
http://searchenginewatch.com/article/2100605/Survey-Predicts-Google-Will-Pass-Twitter-LinkedIn-in-2012