After the resolution of bug #140582 (kde-base/kdm removed from kdesktop DEPEND) kde-base/kdebase-startkde doesn't pull in kde-base/kdm in dependency list anymore.
So in a new installation, if i emerge a basic KDE environment (like explained in http://www.gentoo.org/doc/en/kde-config.xml ) with
# emerge kdebase-startkde
kdm will not be installed, that pull in problems when i follow the "Graphical Login" configuration section in the above guide. (the user must install kdm manually to avoid this)
I think it should be correct to add kdm to kdebase-startkde DEPENDS list, to ensure a proper basic installation of KDE.
p.s. Sorry for my BAD english :P
I don't think startkde needs kdm. I know lots of setups where kdm is not used at all.
If you want a not-so-minimal KDE base system, I'd suggest using kdebase-meta rather than kdebase-startkde.
The document makes no reference to split ebuilds, only to monolithic ebuilds.