Just one month into its launch, Google+ has seen extraordinary growth, netting some 20 million unique visitors.  Still, it faces several key challenges before it can become the dominant force in social media.  Online metrics company ComScore said that of the 20 million users, five million of those are from the United States.  “Google+ is on an unprecedented growth trajectory over its first three weeks, reaching 20 million visitors faster than any site in recent memory,” Comscore Vice President Andrew Lipsman said.  The estimate comes a week after Google CEO Larry Page said that the company already had accumulated 10 million registered users. While registered users and unique visitors are not necessarily the same thing, that growth has been nothing short of impressive.

While the rate of growth is unparalleled, the social network is still small when compared with its rivals such as Facebook and Twitter, which have 750 million and 200 million registered users, respectively.  Google+’s success will depend on how Google “converts this strong trial base into regular users,” Lipsman warned.  While competitors Facebook and Twitter have become online destinations in themselves; more than 50 percent of traffic coming to Google+ is initiated by visits to Google or Gmail, according to Experian HitWise.  YouTube is a significant referrer.

Writing on the DVice website, Raymond Wong says that “Google+, the new guy on the social networking scene isn’t doing too bad.  After Google CEO Larry Page announced last week that Google+ had 10 million users in a mere two weeks, it appears they’ve added another 10 million users.  Talk about being the hottest thing in town.  People said that Google couldn’t build a social network that anybody would give two cents about, but somehow they’ve managed to do just that.  According to an independent comScore report, the new Google+ social network has hit 20 million unique visitors in three weeks.  Some have called Google+ a Facebook rip-off.  Some have joined simply to see what the buzz is all about, much like how everybody started Google and for a brief moment in time and then disappeared into oblivion. For now, none of that matters.  Google+ is gaining more users everyday, and Google is sure to be super excited by all the signups.”

“So while we have a lot of work still to do, we are really excited about our progress with Google+,” Page said, noting that Google will re-focus on its core products and on new innovations.  “Google+ is also a great example of another focus of mine — beautiful products that are simple and intuitive to use and was actually was one of the first products to contain our new visual redesign.”  Google+ isn’t Google’s first expedition into the world of social media and its excitement over having 20 million Google+ users may be early.  Google introduced Google Buzz in February 2010 and immediately saw user numbers swell; it was later panned.

Reports are that Google will, unlike Facebook, host games on its own servers — this could make them faster and less prone to glitches.  The Google+ code mentions a gaming platform, and the company has reportedly invested as much as $200 million in the leading social gaming company Zynga.  There has been no official announcement about if and when the Google game platform will launch or how it will be designed.

Facebook is still beating Google+ in time spent on a social network.  HitWise research director Heather Dougherty said the average visit time for Google+ is five minutes and 50 seconds, compared with almost 22 minutes on Facebook.  Dougherty also examined how users arrived at Google+.  Google.com (at 34 percent) and Gmail (at 26 percent) account for 50 percent of all traffic to Google+; another six percent come from YouTube and Google Profiles.  Facebook ranked third among websites visited immediately prior to Google+, an indication that many social-network users have multiple accounts.  Google+ ranks as the 42^nd most visited social networking site in the United States, and was the 638^th most visited website.  Broken down by region, most of Google+ visitors are from Los Angeles, New York City and San Francisco (in descending order).