Someone

root /etc #  emerge -uDN world

These are the packages that would be merged, in order:

Calculating world dependencies... done!
[ebuild  N    ] app-arch/lzma-utils-4.32.5  462 kB 
[ebuild     U ] media-sound/alsa-headers-1.0.16 [1.0.14] 2,662 kB 
[ebuild     U ] net-misc/rsync-2.6.9-r6 [2.6.9-r5] USE="acl -ipv6 -static -xinetd" 0 kB 
[ebuild     U ] dev-util/desktop-file-utils-0.15 [0.14-r1] USE="-emacs" 341 kB 
[ebuild     U ] dev-libs/libxml2-2.6.31 [2.6.30-r1] USE="python readline -bootstrap -build -debug -doc -examples% -ipv6 -test" 4,624 kB 
[ebuild     U ] app-text/poppler-0.6.3 [0.6.1-r1] USE="jpeg zlib -cjk" 1,263 kB 
[ebuild     U ] sys-devel/m4-1.4.11 [1.4.10-r3] USE="nls -examples" 684 kB 
[ebuild  N    ] app-admin/sudo-1.6.8_p12-r1  USE="offensive pam -ldap (-selinux) -skey" 0 kB 
[ebuild  N    ] media-plugins/gst-plugins-libpng-0.10.6  0 kB 
[ebuild     U ] sys-devel/automake-1.10.1 [1.10] 897 kB 
[ebuild     U ] media-libs/alsa-lib-1.0.16 [1.0.14a-r1] USE="midi -alisp -debug -doc" ALSA_PCM_PLUGINS="adpcm alaw asym%* copy dmix%* dshare dsnoop empty%* extplug file hooks iec958%* ioplug%* ladspa lfloat linear meter mulaw multi null plug%* rate route share shm softvol%*" 764 kB 
[ebuild     U ] sys-apps/coreutils-6.10-r1 [6.9-r1] USE="acl nls (-selinux) -static -xattr" 3,670 kB 
[ebuild   R   ] net-irc/weechat-0.2.6  USE="perl python ruby* spell ssl -debug -lua" 0 kB 
[ebuild   R   ] dev-lang/swig-1.3.31  USE="java perl php python ruby* -doc -guile -lua -mono -ocaml -pike -tcl -tk" 0 kB 
[ebuild     U ] media-sound/alsa-utils-1.0.16 [1.0.14] USE="midi nls" 992 kB 
[ebuild   R   ] gnome-base/gnome-vfs-2.20.1-r1  USE="acl avahi* hal ssl -debug -doc -gnutls -ipv6 -kerberos -samba" 0 kB 
[ebuild     U ] media-sound/exaile-0.2.13 [0.2.11.1] USE="aac alsa gnome ipod jpeg libsexy mad nls ogg oss png%* vorbis -cdparanoia -equalizer* -flac -libnotify -musepack" 1,239 kB 
[ebuild  N    ] xfce-base/thunar-0.9.0-r2  USE="X dbus gnome hal pcre startup-notification trash-plugin -debug -doc -exif" 0 kB 
[ebuild  N    ] kde-misc/kdnssd-avahi-0.1.2  USE="xinerama -arts -debug" 0 kB 
[blocks B     ] sys-apps/mktemp (is blocking sys-apps/coreutils-6.10-r1)
[blocks B     ] >=sys-apps/coreutils-6.10 (is blocking sys-apps/mktemp-1.5)

Total: 19 packages (11 upgrades, 5 new, 3 reinstalls, 2 blocks), Size of downloads: 17,594 kB

!!! Error: The above package list contains packages which cannot be installed
!!!        at the same time on the same system.