Before version 2.3.60, running `emerge --sync` as a non-root user (in the portage group) worked, so long as that user had write access to the tree(s) being synced. This no longer works in 2.3.60 (after the patch for bug 636798 was committed), because portage tries to create an arbitrary file in /var/log (/var/log/.emerge.log.hardlock-<HOSTNAME>-<PID>). This obviously does not work when emerge is run as a non-root user.
*** This bug has been marked as a duplicate of bug 678278 ***