Masked by profile /var/paludis/repositories/gentoo/profiles/hardened/linux/package.mask Can't be used on hardened. See upstream, http://developer.skype.com/jira/browse/SCL-616 The link is dead, also worksforme on PaX-enabled kernel and hardened-toolchain built userspace.
Skype is indeed masked. The selfchecking it did was the reason for introducing XT markings though. Using XT marking skype should work as expected so it should be considered for unmasking.
Rather than unmasking skype, it seems skype itself will soon be obsolete, see bug 608174
Skype was dropped in git commit d7c8833dec2b13923edd6b31247292679f1ecc63