Facebook bought the domain fb.com last year and it's just been revealed that they shelled out a lovely $8.5 million for it. It's supposedly being used for company email.
Facebook announced earlier this year that it's revamping its 'Messages' function. Even though Mark Zuckerberg's maintained that it's not email, but it assigns you a facebook.com address and organizes all of your communication into one inbox (or customizably into more). However, Facebook employees already have @facebook.com email addresses. Reportedly, the fb.com domain is to reassign employee email addresses so Messages can roll out. Facebook bought it from the American Farm Bureau Federation for $8.5 million. This is the second high profile domain buy they've done. The first was the purchase of facebook.com for $20,000 in 2005, when they were changing from thefacebook.com to just facebook.com.