What happened?

Some of the decline may be explained by the fact that a Google+ profile was created automatically when people registered for Google. That alone would generate an impressive number of profiles, but wouldn’t necessarily lead to active use of the social media platform. According to Forbes, just 6.7 million users have 50 or more posts ever, and only 3.5 million have 50 or more posts in the last 30 days.

The apparent failure of Google Plus brings into question two things we thought we knew about the Internet era:

Privacy

First, we thought that a better approach to privacy would provide a competitive advantage. The idea here is that savvy consumers crave privacy and consequently would flock to any social network, which offered better privacy options. Google Plus’s main advantage relative to alternative social networks Facebook (FB) is that it had a far more customizable and intuitive system in the form of circles. As such, Google Plus did a great job at easily allowing a user to manage the privacy concerns inherent in multiple identities. For example, I am a mother, a marketing professor, a mentor, an economist, an alumni of various schools across the world, and a member of the family Tucker.

I do not want my students knowing that I squabble ridiculously with my sister. I do not want to bore my professional colleagues with my incredibly cute babies’ photos. I do not want my mentees to hear me spouting something less than inspiring about my inability to do simple things. And Circle allowed me to tackle that.

This was the key “point of difference” with Facebook. However, despite research suggesting that consumers are deeply worried about controlling the sharing of information on Facebook, and that for me at least this system of Circles made intuitive sense for some of the most pressing privacy concerns people face on a social network, this new privacy system was not enough to induce viewers to switch to Google Plus.

Stickiness

The second assumption was that Google can succeed at anything it likes because it is such a prominent search engine. The rationale was that as we all use Google (GOOG) as a search engine therefore it had an inherent advantage in any other web business. However, the failure of circle shows the weakness of Google, and in some sense, the lack of stickiness it enjoys as a platform.

Though many people use Google as a search engine and for email, those relationships were simply not sufficient to persuade them to shift from Facebook to Google+. It appears that as consumers we are very content to use multiple different platforms for different purposes rather than entrusting our lives to a single platform.

While the future remains unclear for Google plus, these are important lessons for other social media platforms. The assumptions about social media that we started with a few years ago don’t necessarily hold true today.

Catherine Tucker is a marketing professor at the MIT Sloan School of Management.