ComScore bases its estimate on a global measurement panel of 2 million users. Google hasn't confirmed the numbers, but last week, Google CEO Larry Page said the service had more than 10 million users sharing 1 billion items per day.
"I've never seen anything grow this quickly," ComScore analyst Andrew Lipsman told the Wall Street Journal.
So, now what? It's clear that Google+ isn't a flop like its immediate predecessor, Google Buzz. With a steady base of users investing time in Google+, we can start to look at where the social network will be going next:
Business and Brand Pages
To the dismay of brands and businesses who want to reach the quickly-growing Google+ audience, Google is restricting its social network to personal use and banning accounts that appear to be tied to a business.
Google promises to have a system for all businesses and brands in the coming months. "The platform at the moment is not built for the business use case, and we want to help you build long-term relationships with your customers," Google Group Product Manager Christian Oestlien wrote. "Doing it right is worth the wait."
How exactly Google+ will attack the Facebook gaming juggernaut is unclear, but Google has reportedly pumped hundreds of millions of dollars into Farmville maker Zynga, and is rumored to be creating a separate "games" stream in Google+ so your friends won't have to hear about the status of your farm unless they want to.
Integration With Other Services
Over time, Google is expected to hook its existing services into the social backbone of Google+, allowing users to share Google Docs documents, YouTube videos, and more with the circles they've created on the social network. For now, integration is limited to the notification boxes that appear atop Gmail, Maps, and other services, but over time expect Google+ tie-ins to grow deeper.