The ubiquitous social networking platform continues to grow like wildfire and last week unseated Google as the Web traffic leader for the first time since 2007.According to data from Experian Hitwise, Facebook was the most visited Web property in the U.S. last week. The social network that Mark Zuckerberg hatched in his Harvard dorm room drew 7.07% of Web visitors during the week ending March 13. The runner up was Google with 7.03% of Web traffic. The last time that the search leader wasn't atop the traffic ranking was in 2007 when MySpace took the leadership mantle for its one shining moment.

That MySpace tumbled from so far from its Icarus-like ascent over Google could be viewed as a cautionary tale. A potentially significant difference in the staying power of Facebook is the increasingly widespread use of Facebook Connect as a default authentication agent for SMBs and start-ups. The halo effect of this practice to extend and support Facebook's reach can't be overlooked.

But if Facebook (as well as other social networks) has an Achilles heel it may be the perception that it's a diversion that saps workplace productivity. An example of this perspective is evident in the findings of a recent survey of Missouri companies conducted by AAIM Employer's Association. According to the findings, almost 80% of Missouri companies either prohibit or restrict use of social networks during working hours and 25% of companies block access to Facebook, MySpace, LinkedIn. While that may be true, Facebook boosters should point out that if Facebook outpaces Google with some users blocked out for 40 or more hours per week, the Hitwise traffic may actually be understating the gains it has made on Google.

One avenue those employers aren't blocking is access via mobile devices. According to a recent comScore report, mobile visits to Facebook have grown by more than 100% and visits to Twitter by almost 350% over the past year. Eye-opening numbers like that led none other than Google's Eric Schmidt to say in his keynote address to the Mobile World Congress last month that "The confluence of these three factors (computing, connectivity, and the cloud) means your phone is your alter ego, an extension of everything we do. Here, right now, we understand the new rule is 'mobile first' in everything."

Google may see mobile and the future, but the search leader is hardly alone and the competition of share of visitors (not to mention share of wallet) only stands to get more heated.

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