Normals that are generated on the fly are only correct if polygon
vertices are oriented properly. Some programs do not consistently
order these vertices -- I know that Lightscape and Autocad have this
problem, for instance. You can use the ShapeHints node to tell the
browser about the vertex ordering, but for large files this may not
be feasible.
So, yes, the lighting is off, but normals affect more than this. The
result of removing normals from a file that is oriented incorrectly
is to have half the face essentially dissapear.
James