I would imagine that they are generated randomly, probably with a machine. Similar to the way people come up with phone #'s, they probably have to be precise and make sure no two players get the same FC. If you want mine mine is below. I only have one friend, dark*star but I am eager to gain more.
"In reality, hope is the worst of all evils, because it prolongs man's torments." ~Friedrich Nietzsche Hope* FC: 4170-3637-3845