jonas@noggin /usr/portage/x11-libs/libwnck $ sudo emerge libwnck -pv

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

Calculating dependencies   
!!! All ebuilds that could satisfy "libwnck" have been masked.
!!! One of the following masked packages is required to complete your request:
- x11-libs/libwnck-2.16.2 (masked by: ~amd64 keyword)
- x11-libs/libwnck-2.16.1 (masked by: ~amd64 keyword)
- x11-libs/libwnck-2.14.2 (masked by: ~amd64 keyword)

For more information, see MASKED PACKAGES section in the emerge man page or 
refer to the Gentoo Handbook.

jonas@noggin /usr/portage/x11-libs/libwnck $ cat libwnck-2.16.2.ebuild | grep KEYWORDS
KEYWORDS="~alpha amd64 ~arm ~hppa ~ia64 ppc ppc64 ~sh sparc x86"
jonas@noggin /usr/portage/x11-libs/libwnck $