Microsoft's Bing debuted last May, and since then, it has marketed relentlessly in an attempt to sell itself as a worthy rival to the Google search engine. Bing's latest marketing tactic, which was to drive traffic to its official Facebook fan page by offering free FarmVille cash, brought in over 400,000 fans to Bing in one day.

The offer has since ended, but Christopher Heine of ClickZ reported the numbers: "Its Facebook fans currently total 564,000, which puts Bing ahead of search rival Google's 524,000. Facebook metrics firm AppData shows that 28.7 million people played FarmVille on Tuesday. Therefore, 1 to 2 percent of players clicked through the ad to become fans of Bing."

And while Google still out performs Bing in terms of usage, Heine suggests that Bing's true motive behind the drive of traffic "was to gain a bigger Facebook presence" due to Microsoft having recently signed FarmVille to MSN Games.