I would agree with Francois that people with whom one might happen to work, and perhaps engage in some chats with, might not be considered actual friends. Acquaintances yes. It's easy to say that our acquaintances far out number friends for most of us.
With regard to what Francois said about his unfortunate experiences with hiring friends, I can relate in a sense. That's never happened to me, but I've already resolved that, should an opening ever occur in my department, I would not hire a friend. I think it opens up all kinds of uncomfortable possiblities.