This is a design decision made by Canonical. They want the buttons on the
left for two reasons: they are covered by notifications at times and they
have plans to put something on the right with 10.10. You can edit gconf
manually to place the buttons on the right or my personal favourite is to
use Ailurus and it has a setting to use GNOME default buttons.

Ailurus is useful for many things and is worth installing. It is like Ubuntu
Tweak. I have both installed, just because I am a KDE user and you can't
have too much of a good thing (changing settings). ;)

Auilurus: http://code.google.com/p/ailurus/

Edit gconf: http://ubuntuforums.org/showthread.php?t=19413