chmod g=u does not work as expected. The write privilege is removed. 
This not very logical and differs from other Unix platforms (I tried Irix, 
Solaris and AIX). 
(I think this was done for security reasons. But this is not Windows. I want 
to shoot myself in the foot! :) 
 
> touch xxx 
> chmod 700 xxx   
> ls -l xxx 
-rwx------    1 user   user          0 Apr 21 15:24 xxx 
> chmod g=u xxx 
> ls -l xxx 
-rwxrwx---    1 user   use          0 Apr 21 15:24 xxx 
> chmod o=u xxx 
> ls -l xxx 
-rwxrwxr-x    1 user   user          0 Apr 21 15:24 xxx