"Friends" in the Broad Sense of the Word

I was writing a letter to an old friend tonight and as I went to sign my name, I debated whether to add my last name as well as my first. Then it occurred to me, if I have to sign my full name to an email to a friend, then they probably aren't very close friends to begin with. Which made me think, again, on how lightly people use the word "friends" these days. I have even heard some people refer to others with that term even while discussing how they can't stand them. Silly at best...sad at worst...