bug#4449: 23.1.50; ns: variable-pitch uses a strange font

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

I downloaded the build of Emacs.app 2009-09-16¹ and found that the
variable-pitch face (used for example in C-h C-a and AUCTeX for
sectionings) is using a strange font: Skia.

Previously it used Helvetica. Skia is horrible in many aspects. I wonder
if there is a bug in emacs that causes this change.

Footnotes: 
¹  http://atomized.org/wp-content/cocoa-emacs-nightly/Cocoa%20Emacs%2023.1.50%20CVS%202009-09-16.zip