From what I've seen, the "unavailable" fans are Facebook friends from different servers. So this person has a lot of Facebook friends that play and watch the games. If they're all legit accounts is a different issue.
motrin answered that.
There are the server friends, where you can see the profiles and maybe send a friend request to them
the fb friends (you can also see them sometimes but not send "add friend")
and those those "unavailable" who are also fb friends but cannot see more info.
Anyway, it's not a hack or anything.