I went to remove someone from my friend list, and it removed all my friends.
Are you sure? Your list shows 20 friends now. We've wanted a way to remove more then one friend at a time for a long time now. This could be good news for some of us.
Have you clicked the invites tab by accident on your friends list? You can make everyone disappear instantly by doing that.
It did all vanish for a while, but did eventually return.