Facebook bought the domain from the American Farm Bureau Federation, which uses fb.org as its primary domain. At its annual meeting in Atlanta, the non-profit revealed that it earned $8.5 million on the sale of fb.com.
The last high-profile domain purchase by Facebook was for Facebook.com, way back when it was known as TheFacebook. The company paid $200,000 in August 2005 to acquire the domain. FB.com is also used as the domain for Facebook employee email addresses.