If the Amazon Kindle's passage-sharing Twitter integration wasn't social enough for you, the outfit just unleashed a new option: @author. The new feature uses Twitter as a springboard to connect writers to their fans, giving users a chance to nitpick their favorite authors line-by-line. If you've ever shared a quote using the Kindle, you know the drill: highlight some text and type out your tweet -- just make sure you preface it with the @author marker. This limited beta is launching with only a handful of writers, but between Robert "Rich Dad" Kiyosaki and Brad "Identity Crisis" Meltzer, w
