I have always felt that photography's greatest strength was the illusion of reality it represents. You see it in a photograph and there is an assumption that it is real, that it really happened (This assumption is of course false because photographs are not reality but a subjective statement created by the photographer). The fact that it is perceived as real gives the photograph special power that painting/drawing etc can never obtain.
The problem with the current digital age in photography is that this illusion of reality is being lost. People who view images in the year 2009 know that in photoshop you can pretty much create anything you want. Is the photo real? Did it really happen? No it is just a photoshop illusion, it is not real.
Photography's greatest strength is being diminished by the advent of digital manipulation of imagery.