Google on Monday announced a new milestone for its Google+ social networking platform. Vic Gundotra, the company’s senior vice president of engineering, revealed that Google+ is now home to more than 400 million members and, despite arguments that claim the service is a ghost town, it now attracts 100 million active monthly users. “It was only a year ago that we opened public sign-up, and we couldn’t have imagined that so many people would join in just 12 months,” Gundotra wrote. Facebook, Google’s main competitor in the social space, has more than 900 million active monthly users. Read the full story at Boy Genius Report.