Who Is the Author of a Comic?

Comics are often extremely collaborative, many owned by companies, not individuals, so who are the real authors? How do we define author in the case comics? Does Frank Miller or Joh Romita Jr bear the responsibility of visuals in Superman Year One? How did a Gisèle Lagacé comic almost have its cover redrawn and recolored by the printer? What is an auteur, a mangaka, a gensakusha? Why should we, as audience, fans, or professionals, care?