I think the following 2 file names are not intentional, isn't it ? :
tfoerste@n22 ~ $ ll /usr/share/applications/_usr_bin_*
-rw-r--r-- 1 root root 214 Nov 29 10:48 /usr/share/applications/_usr_bin_designer-qt-gui-4.desktop
-rw-r--r-- 1 root root 221 Nov 29 10:48 /usr/share/applications/_usr_bin_linguist-qt-gui-4.desktop
I agree it's ugly, but those names are generated by make_desktop_entry (eutils.eclass) when the first argument (the binary to run) is an absolute path.
Starting from 4.8.0 (soon in portage), qt-gui and qt-assistant no longer pass absolute paths to make_desktop_entry(), thus this can be considered fixed.