Look at the trailer for the upcoming film, "Easy A" and imagine what this could do to the meaning of a favorite atheist symbol. If this ends up being a hit, people will likely mistake our symbol some sort of odd promotion of the film. Admittedly, almost nobody outside the atheist community seems to recognize this symbol, but now they might assume we are diehard fans of this flick.
Update: Yes, I am fully aware that the red A stood for adulterer long before this film. My concern is that the film will give people yet another way to confuse the meaning of our A. I thought that this went without saying when I posted this; I was wrong.