How come no-one has discovered the city of Akkad yet ?

Apart from the obvious answer that nobody has yet looked in the right place, there are a number of likely reasons.

1) Shifting rivers: the course of the Euphrates seems to have shifted over history. For all we know, the site of Agade (Akkad) may be part of the present-day riverbed.

2) Abandonment and decay: the Akkadian Empire collapsed amid conditions of severe climatic change after the death of Naram-sin's son Shar-kali-sharri. The invading Gutians may have sacked and abandoned it, and knowledge of its location would have been lost:

http://en.wikipedia.org/wiki/Akkad#Collapse_of_the...

3) No till: if it was never resettled after the catastrophe that caused its abandonment, it would not have left a 'tell' or 'till', the characteristic mound that hints at the presence of an ancient city. Archaeologists have learned to target tills as a relatively quick way to discover ancient cities.

4) Someone lives on the site: if the site is currently occupied, archaeological investigation of it is difficult or impossible.

Those seem to be the most likely reasons.

I'm working as hard as I can! Cut me a god damn break!