According to Google Trends, Facebook has just surpassed MySpace in US search volume for the first time ever.

This time last year, MySpace was seeing over 4x the search volume of Facebook, and as recently as October 2008 MySpace was seeing over twice the US search volume as Facebook, according to Google. While search volume does not offer insight on user behavior after the click, it is a good general indicator of relative growth and retention trends.

For further context on the changing landscape of US social networking behavior, here’s the 5 year chart on search volume. While MySpace held a commanding lead for several years, 2008 was clearly a banner year for Facebook’s growth.

The battle between Facebook and MySpace for US users has been getting much more tight lately. In December, web metrics firm Compete said Facebook had more US unique visits than MySpace for the first time, though data from Hitwise showed MySpace with a strong lead.

Facebook surpassed MySpace in global search volume back in spring of 2008. Since then, Facebook’s lead has only continued to increase. December data from Comscore showed Facebook reaching 220 million unique users worldwide, compared to 125 million for MySpace.