The viral growth of Google+ has slowed somewhat over the past few days, but my new-and-improved 1,000 surname model shows that more than 750,000 people joined the site on Monday, bringing the total user base to just under 18 million.

Last week we saw two days where more than 2 million signed up in a single day. If that rate had continued, Google+ would have reached 20 million users by last Sunday night. But the last four days have averaged only 948,000 new users and yesterday the site added only 763,000. Yesterday's growth of 4.47% was the slowest viral growth since Google opened up invites back on July 6th.



Google hasn't started marketing Google+ through any of its other channels yet. More than a billion people worldwide use Google products, including its top rated search engine, YouTube, and Blogger. Chairman Eric Schmidt says the vision is to integrate Circles and sharing with all the other Google properties. When that happens, you will likely see millions of people joining Google+ every day for some period of time.

Source: Paul Allen @ Google