This discussion comes up a lot. Basically, by the rules Dwarves need to get the exotic weapon proficiency feat to use it. Many DM's Rule 0 it, however.
Personally, I think Dwarves get a lot of cool racial abilities... and it's not that big of a deal for a fighter to use up one of his many feats to pick this up.
I guess it's sort of saying that even within the Dwarven community, the Dwarven Waraxe is a pretty special weapon that not every dwarf is able to wield...