Business cards are the first impression a person makes with their audience. Likewise it has to be an extension of yourself. In the spot where they asked me to put my occupation, I so wanted to put 'bullshitter'.
Writer/Author won out, but just barely. When they asked for a website, I of course, put this one. Even made a new e-mail address for all my writing needs.
So when someone asks for the name of my new book, I can just give them the card. Much classier than scribbling the note on a piece of paper. Makes me seem less desperate, more professional... yeah, that's it.