• by Erik Sass , Staff Writer @eriksass1, December 29, 2011

After months of skepticism and nay-saying from doubters like myself, Google+ appears to be establishing itself as a viable social network and possibly even a competitor to Facebook (even though doctrinaire users will remind you that it is not supposed to be a social network or a Facebook competitor, according to Google executives).

The latest good news for Google+ comes in the form of user estimates from Paul Allen, the founder of Ancestry.com, and comScore, which needs no introduction. Using the surname-based estimate system created by Allen, the Ancestry.com folks speculate that Google+ has 62 million registered users; meanwhile comScore says that Google+ attracted 67 million unique visitors in the month of November alone.

Of course, none of this data tells us anything about the degree of engagement among these users, including for example the number of visits per month, the duration of the visits, the frequency of content-sharing of different types, and so on. But the number of visitors/users in these estimates is up sharply from earlier estimates of 18 million users at the end of July, suggesting more than three-fold growth in less than six months.

In fact, Allen forecasts that if current growth rates hold steady, Google+ could pass 400 million users by the end of 2012, at which point nobody will deny that the network effect has kicked in, making it a real rival to Facebook (except, perhaps, those intransigent Google executives).