Google+, which has struggled to gain traction against social networking behemoth Facebook, has lost its leader and co-founder,leaving industry analysts to wonder about the future of Google’s foray into social media.

On his Google+ account Thursday, Vivek “Vic” Gundotra, Google senior vice president for social, offered no explanation for his departure after eight years and gave no indication where he will end up next.

Google CEO Larry Page later wrote that Gundotra “built Google+ from nothing. … In the meantime we’ll continue working hard to build great new experiences for the ever-increasing number of Google+ fans.”

Last year, Google+ reported that it had 540 million monthly active users, compared with Facebook’s more than 1 billion active users.

Like Enderle, Tim Bajarin, president of Creative Strategies, believes that Google is not ready to pull the plug on Google+. But it’s not succeeding in its current incarnation, Bajarin said.

“Google+ clearly has not taken off anyway near what Google expected,” Bajarin said. “But I don’t get the impression that Google’s ready to discontinue it. Google+ as a social media tool didn’t work. But it’s been moving more and more toward a Google tool used as a hangout for video conferencing for business. I wouldn’t be surprised if it’s de-emphasized as social media and fine-tuned as a business communications tool.”

In his Google+ post announcing his departure, Gundotra thanked Page and the Google+ staff “who built social at Google against the skepticism of so many. The growth of active users is staggering, and speaks to the work of this team. But it doesn’t tell you what kind of people they are. They are invincible dreamers. I love them. And I will miss them dearly.”

Finally, he thanked the millions of Google+ users. “Without you, this social network wouldn’t exist,” Gundotra said. “Your support for Google+, and for me personally, is something I will never forget.”