Wikileaks has leaked all sorts of interesting documents like scandals related to the economic collapse of Iceland etc. It's just that this current affair is of such a magnitude that it overshadows all other leaks.
It's also a matter of global interest. If these where cables leaked by Belgians written in German they wouldn't have received the same attention because no one really cares about Belgium, and Belgium certainly has little to offer on the matter of global politics that could be of interest and have implications for all other western nations.
"What is interesting about this is not the damage it does, which will likely be minimal as it's really just embarrassing."
I believe that you underestimate the insanity of some of the individuals that have been insulted. I'm certain that many of these megalomaniacs put their ego at such high regard that they go to war and kill people for less then a personal insult.
Still, I'd rather see a war fought over humanitarian values like freedom of speech and the rights of wikileaks then for money and oil.
It's also a matter of global interest. If these where cables leaked by Belgians written in German they wouldn't have received the same attention because no one really cares about Belgium, and Belgium certainly has little to offer on the matter of global politics that could be of interest and have implications for all other western nations.