System Information
Mac OS X 10.11.4, Intel Iris 5100

Blender Version
Broken: 2.77 22a2853 (also at least on 2.75a)

Short description of error
Basic (default) sphere exported as OBJ has arbitrary number of exported normals, depending on the object's translation in the Blender editor.

Exact steps for others to reproduce the error
In default scene (fresh install), add a UV sphere. It should be centered at (0, 0, 0) and (default) flat shaded. Select sphere, and export as OBJ, being sure to check "Selection only," "Write Normals," "Triangulate Faces" (all other options default). Count the number of lines in the exported OBJ file (I used a text editor with line numbers, showing 1985 lines). Now, in Blender, move the sphere to an arbitrary location; I chose (1, -3, 0). Perform the same export process, and count the number of lines. (I get 2014 lines.) After careful study and programmatic parsing, it seems the only difference is the number of normals included in the file.