Hi Brendan,

As Burr mentioned it's not the STL file that is a problem, you can send the 3d print guy a super dense mesh and the end result will be the same.
This is a stepping phenomena that's common with 3d printing because the way the material is layered on step by step even with the Replicator with a 0.1mm (0.004") resolution.
The effect is more visible on curved areas, imagine a tiny staircase and it's more obvious on items with gentle curves such as spheres which your model shows.

Usually model guys will over size areas to allow for sanding to achieve a smooth surface.

There are other 3d printing technologies out there that will do a finer job unfortunately the price increases also. To get a better idea check out Shapeways they have variety of materials and processes to give you an idea on what's out there http://www.shapeways.com/materials?li=nav

Hope this helps.

Cheers