I'm quite sure that Keira's agency and the lady herself wouldn't be too partial to sending autographed headshots to collectors who will then try to make money by selling them to genuine fans.
I've got four autographs, including one headshot. I have them because I wrote her a letter about how I admired what she was doing, and because it was evident that I was just a fan. Her agents are doing the best job they can, getting pictures signed by Keira. She's a busy lady who receives a tonne of fan mail these days. I think she rocks all the more for reserving autographs for fans, not collectors.