????Facebook has dethroned Google! Sort of! Well, ok, not really. For the week ending March 13, the social networking site got more traffic than its competitor in the United States, according to a blog post by industry tracker Hitwise. But be careful how you slice your numbers. While many pundits may use this data to validate predictions that Facebook will eventually beat Google (GOOG) at its own game, the social networking startup has yet to pull ahead in any real sense.

????Here’s what’s true: for the first full week, more Americans typed "Facebook.com" into their browser than "Google.com." But these figures account for only a portion of Google’s web properties. They don’t measure Gmail or YouTube at all. Looked at in isolation, YouTube alone was the fifth most visited website during the week ending March 6, according to Hitwise.

????Even if you do compare the use of Google’s search site to the overall use of Facebook, you must consider how people tend to use Google’s search product: When’s the last time you plugged the entire URL into your browser? Many Google searchers instead rely on boxes embedded in their web browsers or use Google’s search product on another website like TechCrunch.com.

????The more surprising thing about Hitwise’s report is the rate at which Facebook grew. The site’s traffic increased 185% over the past year; Google’s traffic jumped just 9% during the same period. And because Facebook is more of a destination, while Google tends to be a launching point for web use, Facebook’s users stick around once they arrive. This growth is astounding, considering that Facebook has already penetrated so much of the population, and suggests that the site has become the communications platform — akin to the phone or the telegraph before it — that founder Mark Zuckerberg envisioned.

????Another important trend to watch: web behavior is consolidating. Taken together, Facebook and Google (including YouTube, Gmail, and Google Images) accounted for more than 17% of Internet activity for the most recent week available, or nearly one web visit in every five. The largest websites are growing larger and the long tail — all the publishers writing to audiences of a few readers — is growing longer. Meanwhile many mid-size sites like MySpace are losing ground.