As we have all come to expect, Google tops the web traffic graphs every week for as long as I can remember. But not this week. For the first time Google has been knocked off the top spot by, you guessed it, Facebook.

Facebook has taken the #1 US web traffic slot before, but only for a single day. That occurred at the end of last year on Christmas Eve, Christmas Day, and New Year’s Day, but the week ending March 13th, 2010 is the first time Facebook beat Google for an entire week’s worth of traffic.

In total, Facebook managed 7.07% of all US web traffic, while Google only managed 7.03%. Together they achieve a commanding lead over the competition with a combined share of over 14%.

Read more at Hitwise Intelligence

Matthew’s Opinion

Google is no slouch when it comes to keeping track of everything that happens on the web. Such monitoring will include its own share of web traffic and those of its competitors. With that in mind, Google would have seen this coming, and alarm bells would have been sounding on those three days where Facebook went #1 over Christmas.

What’s interesting about this data is how it potentially ties in to the rushed release of Google Buzz. You can imagine Google’s management team getting together in early January and discussing how to combat the rise of Facebook. They likely had predictions of when Facebook traffic could regularly surpass Google’s own, and formulated a plan to keep ahead.

Was that plan Google Buzz? If it was, then it completely backfired. The fallout from that did Google more harm than good, and Facebook has now managed to steal the top spot. Will Facebook now retain the largest market share? I suspect it will bounce back and forth between the two companies for quite a while.