Today's XKCD, "Password Strength," neatly illustrates the research from this paper (PDF) by Philip Inglesant and M. Angela Sasse from University College London, with the ironic conclusion that we've trained our users to use passwords that computers can easily guess and humans can't possibly remember.
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.