Xcode4 dropped PPC support, so when I try building PIL, it throws hate:
Bens-MacBook-Air:Imaging-1.1.7 bkeating$ python setup.py build running buildrunning b
A better way to solve this issue, in my opinion, would be to edit your ~/.profile or /etc/bashrc and add the line:
export ARCHFLAGS="-arch i386 -arch x86_64"
Will save messing around with any future installations (I've just had to do this for installing lots of Perl modules in CPAN)!