"Google+ was a major wake-up call for Facebook," said analyst Rob Enderle of Enderle Group in Silicon Valley.
"They were awakened to the fact that they could be another MySpace; so they suddenly got very aggressive on moving the ball forward so they couldn't get caught," he added.
MySpace was the dominant online social network until it was eclipsed by Facebook.
Google+ combined aspects of Facebook and microblogging sensation Twitter, and promised users that sharing aspects of their lives at the social network would reflect levels of confidentiality granted in real life.
A criticism of Facebook has been that updates are shared with all of one's friends unless a user has gone through a relatively complicated process to create separate Facebook Groups.