After merging coreutils on a desktop (creating a package) and then merging the package on a server, all bins from the package failed on libncurses because it had been merged on a computer with ncurses installed. Don't know if this was introduced in coreutils-5.2.1-r2 or before.
All coreutils-5.2.1 ebuilds I have on my machine depend on ncurses in both DEPEND and RDEPEND
like Stian said, we force ncurses in DEPEND now things like ls use it to get terminal information